The C language, born in 1972, has been at the forefront of system development for over 50 years as a programming language.

Used across diverse fields including operating systems, embedded systems, and IoT devices, it features outstanding execution speed and hardware control capabilities.

This article provides detailed explanations based on public data, covering everything from C language fundamentals to practical applications, engineer market value and salaries, and effective learning methods.

1．What is the C Language? Fundamental Knowledge and Technical Characteristics

The C language is a general-purpose programming language that combines high processing power for direct hardware control with program structures that are easy for humans to understand.

This section provides detailed explanations of the C language’s technical characteristics, from its origins to the present day.

Definition and Historical Background of the C Language

The C language is a programming language developed in 1972 by Dennis Ritchie at AT&T Bell Laboratories in the United States.

Initially created as a language for writing the UNIX operating system, it aimed to implement system programs previously written in assembly language in a more maintainable form.

The C language possesses characteristics as a “mid-level language.” This means it combines the readability and portability of high-level languages with the direct hardware control capabilities of low-level languages (assembly language).

This characteristic enabled the flexibility to be used for a wide range of purposes, from system-level software like operating systems and device drivers to application-level programs.

Static Typing and Compilation Mechanism

Understanding the C language’s technical features requires grasping two important concepts: “static typing” and “compilation.”

What is Static Typing?

Static typing is a method where you declare in advance what type of data (integer, character, floating-point number, etc.) a variable will handle before using it.

For example, writing “int age = 25;” tells the compiler that the variable age is an integer type. This mechanism allows type-related errors to be detected before program execution, preventing unexpected runtime behavior.

High-Speed Execution Through Compilation

Compilation is a method where source code written by humans is converted in bulk before execution into machine language (binary code) that computers can directly understand.

In contrast, interpreter-based languages like Python convert programs to machine language line by line during execution.

The greatest advantage of compilation is execution performance. Pre-optimized machine language is generated, resulting in extremely low runtime overhead and operation several to hundreds of times faster compared to interpreter methods.

This performance difference is particularly evident in iterative processing and calculations involving large amounts of data.

Differences Between the C Language and Related Languages (C++, C#, Python)

Through comparison with languages derived from the C language and those with different design philosophies, we can clarify the C language’s position.

Differences from C++

C++ is an upward-compatible language that adds object-oriented programming features to the C language.

By introducing concepts like classes, inheritance, and polymorphism, it improves maintainability and reusability in large-scale software development.

Much code written in the C language runs as-is in C++, but the reverse is not necessarily true.

Differences from C#

C# is a modern language developed by Microsoft in 2000 that, while based on C language syntax, is designed to run on the .NET framework.

It features automatic memory management (garbage collection) and specifications emphasizing development productivity, primarily used for Windows application development and the Unity game engine.

Differences from Python

Python is an interpreted language that prioritizes writing conciseness and readability.

Adopting dynamic typing, it doesn’t require type declarations for variables, making it designed for easy learning even for beginners. While widely used in AI and machine learning, it significantly lags behind the C language in execution speed.

Comparison Table of Major Languages

Feature	C Language	C++	C#	Python
Execution Method	Compilation	Compilation	Intermediate Language + JIT	Interpreter
Typing	Static	Static	Static	Dynamic
Memory Management	Manual (malloc/free)	Manual + Automatic	Automatic (GC)	Automatic (GC)
Object-Oriented	Not Supported	Supported	Supported	Supported
Execution Speed (Relative)	1.0 (Fastest)	1.0-1.5	2.0-5.0	10.0-100.0
Primary Uses	OS, Embedded	Games, Large Systems	Windows Dev, Unity	AI, Web Dev

As clear from this comparison, the C language has overwhelming advantages in execution speed and hardware control capabilities, though it lags behind other languages in development efficiency and learning difficulty.

2．What is the C Language? A High-Speed Processing Language – 5 Key Capabilities

The C language’s high-speed performance and hardware control capabilities are essential as foundational technology supporting modern IT infrastructure.

This section explains specifically in which fields the C language is utilized and what it achieves.

OS and Kernel Development

One area where the C language demonstrates its greatest power is operating system (OS) development. The kernels (core OS components) of most major OSes used worldwide today are written in the C language.

C Language Adoption in Major OSes

Major OSes like Linux, Windows, macOS, Android, and iOS all employ the C language as their primary language for kernel development.

The Linux kernel in particular has been continuously developed and maintained in the C language since its 1991 release, running on diverse platforms including servers, smartphones, and embedded systems.

The C Language’s Advantages in OS-Level Development

The reason the C language is chosen for OS-level development is its ability to efficiently and accurately describe processes requiring direct hardware resource control, such as memory management and process scheduling.

Direct memory access using pointers and CPU register manipulation are low-level controls impossible to achieve with interpreted languages.

Embedded System and IoT Device Control

Embedded systems refer to computer systems built into home appliances, automobiles, industrial equipment, and other devices to realize specific functions.

The C language has long held the de facto standard position in this field.

The C Language’s Advantages in Embedded Systems

Key advantages include:

• Efficient operation in memory-constrained environments
• Support for real-time control processing requirements
• Implementation enabling minimal power consumption
• Clear separation between hardware-dependent and application portions

Specific Application Examples

Automotive ECUs (Engine Control Units) represent a typical application example.

ECUs need to control engine fuel injection amounts and ignition timing in millisecond units, and the C language is used to realize this high-speed, reliable control.

Microcontroller control programs for home appliances like air conditioners, refrigerators, and washing machines are also mostly written in the C language.

With IoT (Internet of Things) device proliferation, the C language’s importance has further increased.

Requirements demanded of IoT devices, including sensor data collection, communication protocol implementation, and low-power operation, have high affinity with the C language’s characteristics.

Hardware Control and Device Driver Development

Device drivers are software that mediates between the OS and hardware, controlling peripherals like keyboards, mice, GPUs, and network cards.

The C language plays a central role in this domain as well.

Bit-Level Hardware Control

A characteristic of C language hardware control is the ability to operate at the bit level.

For example, when writing values to specific hardware registers, fine control like changing only necessary bits using bit masks and bit shift operations is possible.

NPU and GPU Driver Development

Recently attracting attention is NPU (Neural Processing Unit) device driver development.

NPUs are dedicated hardware for accelerating AI inference processing, and C language-level optimization is essential to maximize their performance.

Development environments like CUDA (NVIDIA) and ROCm (AMD) for GPUs are also based on C/C++.

Applications Requiring High-Speed Processing

Even at the application layer, the C language is actively adopted in fields where execution speed is prioritized.

Database Management Systems

Major open-source databases like PostgreSQL and MySQL are implemented in the C language.

Processing that searches and updates large amounts of data at high speed requires millisecond-level response times, making the C language’s performance indispensable.

Image Processing and Video Encoding

Video compression and decompression processing involves enormous computation amounts, requiring high-speed performance at the language level in addition to algorithm-level optimization.

Image and video processing libraries like FFmpeg and OpenCV are written in C/C++.

Game Engine Foundation

Major game engines like Unity and Unreal Engine write core portions of physics calculations and rendering pipelines in C/C++ to maintain high frame rates.

The C Language’s Role in the AI Era

From 2024 to 2025, while generative AI’s rapid proliferation dramatically increased Python usage rates, the C language’s importance is being reevaluated behind the scenes.

C Language Implementation of Python Libraries

AI model training and inference processing written in Python actually executes through libraries like NumPy, TensorFlow, and PyTorch, whose core portions are implemented in C/C++.

In other words, Python is merely the interface, with the C language handling the actual high-speed computation processing.

Necessity in Edge AI

In edge computing contexts, the C language’s role becomes even more important.

“Edge AI,” which executes AI inference on smartphones and IoT devices rather than in the cloud, requires achieving high-speed processing with limited computational resources and power, making C language optimization essential.

Supporting AI Infrastructure’s Lowest Layer

The background to the C language maintaining 2nd place (10.15% rating) in the TIOBE Index as of December 2025 lies in this fact of continuing to support AI infrastructure’s “lowest layer.”

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3．What is the C Language? A Resource-Efficient Language – 5 Key Advantages

The technical advantages gained by mastering the C language don’t stop at simply “being able to use another language.”

This section explains five fundamental benefits the C language brings to engineers.

1. Overwhelming Execution Speed and Resource Efficiency

The C language’s greatest strength is its overwhelming execution speed. By adopting the compilation method, source code is optimized to machine language level and converted to a format directly executable by the CPU.

This optimization results in virtually no runtime overhead, enabling maximum hardware performance extraction.

Performance Comparison by Language

Feature	C Language	Python	Java
Execution Speed (Relative)	1.0 (Baseline)	10.0-100.0	2.0-5.0
Memory Usage	Minimal	Large	Medium
Startup Time	Immediate	Medium	Slow (JVM startup)
CPU Resource Efficiency	Highest	Low	Medium

Practical Performance Differences

This performance difference appears particularly prominently in loop processing and large-scale data calculations.

For example, when executing 1 million iterations, processing completed in a few milliseconds in the C language can take several seconds in Python.

From a memory efficiency perspective, the C language also excels. By allocating only necessary memory and releasing it immediately when no longer needed, stable operation is possible even in memory-constrained environments.

This becomes a decisive advantage in embedded systems and IoT devices.

2. High Versatility and Platform Independence

The C language possesses high portability independent of platforms and operating systems.

Writing programs in compliance with standardized language specifications (ISO/IEC 9899) allows the same code to run across different environments like Windows, Linux, macOS, and embedded systems.

The C Language’s Application Range

Applications span diverse areas:

• Server-side: Web server and DBMS implementation
• Desktop: OS and system utilities
• Mobile: Native libraries for iOS and Android
• Embedded: Firmware for home appliances, automobiles, and industrial equipment
• Scientific computing: Simulation software

Long-Term Skill Validity

This high versatility means skills once acquired remain valid over long periods.

Not depending on specific frameworks or platforms, they’re less influenced by technology trend changes, contributing to career stability.

3. Deepened Understanding of Programming Fundamentals

Learning the C language enables deep understanding of programming’s fundamental concepts, a significant benefit absent in other languages.

Explicit Memory Management Control

Explicit memory management control cultivates habits of constantly being aware of how programs consume memory and where it should be released.

The series of flows—dynamically allocating memory with the malloc function and releasing it with the free function—doesn’t need conscious attention in languages like Python and Java where memory management occurs automatically.

However, experiencing this “manual management” enables understanding memory leak and performance issue causes at a deep level.

Value of Mastering Pointer Concepts

Mastering pointer concepts is both C language learning’s greatest challenge and most valuable lesson.

Understanding pointers enables concrete visualization of where variables exist in memory and how data is passed during function calls—understanding computer internal operations.

Application to Learning Other Languages

Understanding the C language provides significant advantages when learning other languages.

For example, concepts like Rust’s ownership system and Go’s pointer receivers become far easier to master with C language pointer understanding.

4. Abundant Libraries and Stability from Long History

The C language is a mature language with over 50 years of history since its 1972 birth.

Throughout this long history, enormous amounts of libraries and tools have accumulated, becoming significant assets in practical development.

Comprehensive Standard Library

Standard libraries (stdint.h, stdio.h, stdlib.h, string.h, math.h, etc.) provide functions indispensable to programming: basic input/output, memory management, string manipulation, and mathematical functions.

These are specified as international standards and operate stably across any implementation.

High-Quality Open Source Libraries

High-quality libraries developed by open source communities also exist abundantly.

Combining reliable libraries like OpenSSL (encryption), zlib (compression), libcurl (HTTP communication), and SQLite (database) enables efficient construction of complex systems.

Compatibility in Long-Term Operations

Stability from long history also contributes to existing code readability and maintainability.

The high compatibility where C language code written 20 years ago runs almost as-is with modern compilers is an extremely important characteristic for systems requiring long-term operation.

5. Modernization Through Latest Standard (C23)

While the C language tends to be perceived as an old language, it actually continues evolving continuously.

In October 2024, the latest international standard ISO/IEC 9899:2024 (commonly called C23) was published.

Major Improvements in C23

Key improvements include:

• Security enhancement: Strengthened buffer overflow countermeasures
• Convenience improvements: Extended type inference functionality (auto keyword utilization)
• Standard library expansion: Addition of new header files
• Improved concurrent processing support: Enhanced thread safety

Adaptation to Modern Requirements

These improvements enable the C language to continue meeting modern software development requirement standards.

Security enhancements in particular serve as factors further increasing the C language’s reliability in IoT devices and critical infrastructure systems.

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4．What is the C Language? A Language with High Learning Difficulty – 3 Key Disadvantages

While the C language offers many advantages, challenges also exist in learning and practical work.

Here we explain three representative C language disadvantages and realistic approaches to addressing them.

1. Syntax Complexity and High Learning Costs

The C language is one of the languages with high initial hurdles for programming beginners. The greatest challenge is the pointer concept.

Pointer Complexity

Pointers are mechanisms for handling memory addresses where variables are stored, enabling indirect data manipulation.

For example, the notation “int *ptr = &value;” means “store value’s memory address in the variable ptr.”

Such abstract concepts are very difficult to understand without understanding computer internal structures, becoming points where many learners fail.

When it comes to application concepts like array-pointer relationships, function pointers, and pointers to pointers, complexity further increases.

Even those experienced with other programming languages (Python, JavaScript) often struggle with C language pointers.

Learning Time Guidelines and Overcoming Strategies

Approximate learning times:

• Basic syntax mastery: About 20-30 hours (variables, control structures, functions)
• Pointer understanding: About 30-50 hours (requires repetitive practice and example understanding)
• Practical program creation: 100+ hours

Effective Overcoming Approaches

Effective approaches for overcoming include starting from small programs and gradually increasing difficulty, using debuggers to visualize memory states, and cultivating habits of carefully interpreting error messages.

2. Bug Risks from Manual Memory Management

In the C language, developers must explicitly perform memory allocation and release themselves.

This “manual memory management” provides high freedom while causing serious bugs.

Memory Leak Dangers

Memory leaks occur when forgetting to release allocated memory.

For example, after allocating memory with the malloc function, forgetting to call the corresponding free function leaves that memory region in an unusable state indefinitely.

In long-running programs, this accumulation can cause system-wide memory shortages.

Segmentation Faults

Segmentation faults are errors occurring when attempting to access invalid memory regions.

Operations like referencing already-released memory, accessing outside array bounds, or referencing NULL pointers cause this.

When this error occurs, programs terminate abnormally immediately, and identifying causes can take considerable time.

Contrast with Garbage Collection Languages

Comparing with languages having garbage collection (automatic memory management), Python and Java automatically reclaim unused memory, so developers barely need to be conscious of memory management.

This difference directly impacts development speed and bug occurrence rates.

Importance of Debugging Tools

Key debugging tools include:

• Valgrind: Detects memory leaks and illegal memory access
• GDB (GNU Debugger): Investigates runtime memory states in detail
• AddressSanitizer: Memory error detection functionality built in during compilation

Actively utilizing these tools enables early detection and correction of memory-related bugs.

3. Low Development Efficiency

The C language tends to require more code volume to implement the same functionality compared to other high-level languages. This is because the C language requires low-level descriptions.

Large Description Volume

For example, even simple string concatenation operations require manually allocating memory in the C language and copying strings using strcpy or strcat functions.

In contrast, Python completes this in one line: result = str1 + str2.

Unsuitability for Prototyping

In development styles like prototyping and agile development that involve rapid trial and error over short periods, this large description volume directly leads to decreased productivity.

For purposes like quickly shaping new ideas and confirming operation, script languages like Python and JavaScript are more suitable.

Productivity Comparison with Modern Languages

Development Phase	C Language	Python	JavaScript
Prototyping Speed	Slow	Fast	Fast
Code Volume	Large	Small	Small
Debugging Difficulty	High	Low	Medium
Library Abundance	Medium	Very High	High

Right Tool for the Right Job

However, this “low development efficiency” can be avoided through appropriate judgment.

Hybrid development approaches are common in modern software development—using the C language for performance-critical portions and hardware control portions, while using high-level languages for business logic and UI portions.

In fact, when Python application performance becomes a bottleneck, rewriting only that portion in the C language (implementing as a Python extension module) is widely practiced.

5．What is the C Language? A Language with Stable Demand – Future Prospects and Market Trends

Analyzing market demand trends and technology trends is essential for judging programming language future prospects.

This section explains the C language’s current market evaluation and future outlook based on public data.

Global Popularity Trends in TIOBE Index

The TIOBE Index is an indicator that quantifies programming language popularity based on search engine search frequency.

It’s widely referenced as highly reliable data showing which languages engineers and companies worldwide are interested in.

December 2025 Rankings

As of December 2025, the C language maintains a high ranking at 2nd place (10.15% rating) in the TIOBE Index.

This ranking isn’t temporary—the C language has consistently remained in the top 3 for over 10 years.

Rank	Language	Rating	Primary Uses
1	Python	23.28%	AI, Data Analysis, Web Dev
2	C Language	10.15%	OS, Embedded, System Foundation
3	C++	10.29%	Game Dev, Large Systems
4	Java	8.86%	Enterprise Development
5	C#	4.45%	Windows Dev, Games (Unity)

Proof of Universal Demand

Notably, even amid Python’s rapid proliferation, the C language’s rating hasn’t significantly declined. This indicates the C language possesses “universal demand” unaffected by specific technology trends.

Source: TIOBE Index (December 2025 edition)

Domestic Engineer Demand and paiza Survey Data

Looking at the domestic market, in paiza’s “Programming Language Survey (2025 edition),” C/C++ ranks top class in engineer job offer rate index.

Languages Companies Seek

This survey analyzes programming language skills companies seek and skills possessed by engineers who actually received job offers, revealing that engineers mastering C/C++ have extremely high job offer rates.

This is proof that the C language is highly evaluated by companies as a “language truly needed in practical work.”

High-Demand Language Fields

Fields with high corporate needs include:

• Embedded system development (automobiles, home appliances, industrial equipment)
• System foundation development (OS, middleware, databases)
• Hardware control (device drivers, firmware)
• Applications requiring high-speed processing (games, image processing)

Stable Demand Amid New Language Emergence

Particularly noteworthy is C language demand remaining stable even as new languages like Go and Rust attract attention.

This indicates the C language remains indispensable for maintaining and operating existing systems and for portions of new development with strict performance requirements.

Source: paiza “Programming Language Survey (2025 edition)”

Reasons for Re-evaluation in the AI/IoT Era

From 2024 to 2025, generative AI’s explosive proliferation seemingly brought a Python-dominant era.

However, examining technology’s deeper layers reveals the C language’s importance is actually increasing.

Necessity in Edge AI and NPU Development

Demand for “Edge AI”—executing AI model inference processing on edge devices (smartphones, IoT devices, automobiles) rather than in the cloud—is rapidly increasing.

Edge devices require achieving high-speed inference with limited computational resources and power, making C language-level tuning essential for this optimization.

NPUs (Neural Processing Units) are dedicated hardware for accelerating AI inference. Device driver and firmware development maximizing NPU performance requires the C language.

C Language Implementation Supporting Python’s Backend

Representative machine learning libraries NumPy, TensorFlow, and PyTorch all have Python interfaces while actual computation processing is implemented in C/C++.

In other words, AI code written in Python operates at high speed because the C language runs behind the scenes.

Infrastructure Foundation in Cloud-Native Era

Many foundational technologies supporting modern cloud infrastructure—Kubernetes, Docker, Linux kernel—are written in the C language.

Even as container technology and microservice architectures proliferate, the C language supports the lowest layer.

Reflection of Invisible Demand

Thus, while latest technology trends like AI, IoT, and cloud superficially spotlight languages like Python and Go, the C language functions as an indispensable presence at the foundational layer.

The TIOBE Index’s stable high ranking can be said to reflect this “invisible demand.”

■Related Reading

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6．What is the C Language? A Language that Increases Market Value – Salary and Job Trends

Programming language mastery directly relates to engineer careers and salaries.

This section explains salary levels for engineers using the C language, primary occupations, and career possibilities opened through mastery.

Average Salary and Compensation Levels for C Language Engineers

According to paiza’s “Programming Language Survey (2025 edition),” company-offered salaries for C/C++ engineers are shown to be high even compared to other major languages.

Trends in Company-Offered Salaries

Survey results show Go language winning first place in offered salaries for three consecutive years, but C/C++ also positions in the upper group, with particularly high expertise being evaluated and corresponding salaries offered in embedded system and system foundation development.

Salary Progression by Experience (Guidelines)

Approximate salary ranges by experience level:

• 1-3 years (Junior): ¥4-5.5 million – Handles basic implementation and existing code maintenance
• 3-5 years (Mid-level): ¥5.5-7 million – Handles portions of design and architecture
• 5-10 years (Senior): ¥7-9 million – Bears overall project technical responsibility
• 10+ years (Expert): ¥9+ million – Oversees multiple projects as system architect or tech lead

Evaluation Through Scarcity

One reason C language masters are valued is the scarcity of engineers with low-level technical knowledge close to hardware.

Engineers deeply understanding concepts like memory management and pointer manipulation demonstrate high value in system performance tuning and troubleshooting.

Source: paiza “Programming Language Survey (2025 edition)”

Primary Occupations and Industries Using the C Language

Occupations leveraging C language skills are diverse. Here we explain specific job duties and required skills for four representative occupations.

Embedded Engineers

Embedded engineers develop software (firmware) built into home appliances, automobiles, industrial equipment, etc.

Specific job duties include:

• Microcontroller control program design and implementation
• Sensor data collection and processing
• Application development on real-time OS (RTOS)
• Collaborative design with hardware
• Power consumption optimization

Primary industries: Automobiles (ADAS, ECU), home appliances (air conditioners, refrigerators), medical devices, industrial robots

System Engineers (OS/Middleware Development)

Occupations developing system foundation software like operating systems, databases, and web servers.

Specific job duties include:

• Operating system kernel development
• Database management system engine portion implementation
• Network protocol stack development
• Virtualization technology and container foundation development

Primary industries: IT infrastructure vendors, cloud service providers, telecommunications carriers

Device Driver Developers

Occupations developing device drivers mediating between OS and hardware.

Specific job duties include:

• Control program creation for GPU, NPU, network cards, etc.
• Direct hardware register manipulation
• Interrupt processing and DMA transfer implementation
• Linux kernel module development

Primary industries: Semiconductor manufacturers, PC/server manufacturers, graphics vendors

Game Engine Developers

Occupations developing engine portions forming game foundations.

Specific job duties include:

• Physics calculation engine implementation
• Rendering pipeline optimization
• Multi-thread processing design
• Memory management mechanism construction

Primary industries: Game companies, game engine development companies (Unity, Unreal)

Career Expansion Through C Language Mastery

C language mastery brings career expansion not limited to single occupations.

Easy Transition to Derived Languages

After mastering the C language, transitioning to derived languages or languages influenced by the C language—C++, Rust, Go—is relatively easy. Particularly, technical commonalities exist:

• C++: Adds object-oriented concepts as the C language’s upward-compatible extension
• Rust: Maintains the C language’s high speed while guaranteeing memory safety through language specifications
• Go: Inherits the C language’s simplicity while supporting concurrent processing at language level

Technical Advantages from Low-Level Perspectives

Acquiring low-level knowledge like memory layout, CPU cache, and process scheduling through the C language enables performance and efficiency-conscious implementation even when designing systems in high-level languages.

For example, when identifying performance bottlenecks in Python web applications, C language knowledge enables inferring fundamental causes like memory allocation and CPU usage, implementing appropriate countermeasures.

Improved Troubleshooting Ability

When system failures occur, the ability to analyze logs and core dumps and identify root causes largely depends on low-level understanding through the C language. This ability significantly increases engineer market value.

Career Paths to System Architect or Tech Lead

Accumulating C language experience opens career paths to roles designing overall system architecture or tech leads guiding technical teams. At these positions, annual salaries of ¥10+ million become realistic goals.

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7．What is the C Language? A Language Effective for Skill Certification – 3 Primary Related Qualifications

Qualification acquisition is effective as a means of objectively proving programming skills.

This section explains characteristics and acquisition benefits for three representative C language-related qualifications.

C Programming Proficiency Test

The C Programming Proficiency Test is a private qualification administered by the Certify Information Processing Proficiency Accreditation Committee. Skills can be progressively proven from C language basic syntax to practical programming abilities.

Test Structure

Level 3

Written test questioning understanding of basic syntax and algorithms. Coverage includes variables, operators, control structures, arrays, and function basics. Pass rate approximately 70%.

Level 2

Written + practical test questioning practical programming ability. Requires implementation of pointers, structures, file operations, and simple algorithms. Pass rate approximately 60%.

Level 1

Practical test questioning applied program design and creation ability. Evaluates implementation based on specifications, debugging, and testing. Pass rate approximately 40%.

Acquisition Benefits

In job-hunting activities, this serves as an effective means of objectively proving skill as evidence of systematically learning C language fundamentals. Listing on resumes enables appealing having systematically learned C language basics.

Fundamental Information Technology Engineer Examination (FE)

The Fundamental Information Technology Engineer Examination is a national qualification administered by IPA (Information-technology Promotion Agency, Japan), one of the most widely recognized qualifications in the IT industry.

Test Characteristics

In the algorithm and programming section, the C language can be selected.

While other languages like Java, Python, and assembly language can also be selected, choosing the C language demonstrates understanding of low-level programming.

Test structure:

• Section A (Multiple choice): General IT fundamental knowledge
• Section B (Multiple choice): Algorithms, programming, information security
• Pass rate: Approximately 25-30% (varies by year)

Career Positioning

As a qualification demonstrating fundamental engineering abilities, the Fundamental Information Technology Engineer Examination receives high corporate evaluation, advantageous in new graduate hiring and young engineer job changes. Some companies also include it as qualification allowance targets.

Source: IPA (Information-technology Promotion Agency, Japan)

Applied Information Technology Engineer Examination (AP)

The Applied Information Technology Engineer Examination is a higher-level qualification above the Fundamental Information Technology Engineer Examination, a national qualification questioning more advanced technical knowledge and practical abilities.

Test Characteristics

While the test questions broad knowledge including system design and project management, selecting the C language in the algorithm and programming section enables proving more advanced algorithm design abilities.

Test structure:

• Morning test (Multiple choice): Advanced IT knowledge overall
• Afternoon test (Written): Applied abilities in design, development, operations
• Pass rate: Approximately 20-25%

Job Market Evaluation

Applied Information Technology Engineer Examination holders can objectively demonstrate abilities as mid-level or higher engineers, sometimes advantageous in salary negotiations during job changes.

Some companies also set it as promotion requirements for positions like system engineer or project leader.

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8．What is the C Language? A Language Requiring Progressive Mastery – 4 Steps for Effective Learning

While the C language is a high-difficulty language, skills can be steadily acquired by following appropriate learning steps.

Here we explain effective learning methods from beginners to practical levels in four steps.

Step 1: Building Development Environment

The first necessity when beginning C language learning is building an environment capable of compiling and executing programs.

Recommended Development Environments

Compilers

GCC (GNU Compiler Collection) is standardly available on Linux and macOS. On Windows, it’s available via MinGW or WSL (Windows Subsystem for Linux).

Integrated Development Environments (IDEs) / Editors

• Visual Studio Code: Lightweight, highly extensible, easy even for beginners
• CLion (JetBrains): Professional high-functionality IDE
• Code::Blocks: Lightweight with simple setup

Online Execution Environments

• paiza Learning: Provides browser-based C language execution environment, enabling learning without environment setup
• Replit: Write code online and execute immediately

Beginner Approaches

For beginners, environment setup often becomes the initial hurdle, so starting with online environments and building local environments after understanding basics is also an effective approach.

Step 2: Mastering Basic Syntax

The stage of systematically learning C language fundamentals. Master the following items in order.

Basic Syntax Learning Items

Variables and Data Types

• int (integer type), float (floating-point type), char (character type)
• Variable declaration and initialization

Operators

• Arithmetic operators (+, -, *, /)
• Comparison operators (==, !=, <, >)
• Logical operators (&&, ||, !)

Control Structures

• Conditional branching (if, else, switch)
• Iteration (for, while, do-while)

Function Definition and Calling

• Basic function structure (return values, arguments)
• Differences between pass-by-value and pass-by-reference

Recommended Materials

Tokyo Institute of Technology’s publicly available “C Language Introduction” is systematized based on academic background. Basic concepts like variables, arithmetic operations, control structures, pointers, and structures are carefully explained.

Step 3: Understanding Pointers and Memory Management

C language learning’s greatest challenge—pointers and memory management—should be understood progressively.

Pointer Learning Items

Basic Pointer Concepts

• What memory addresses are
• Pointer variable declaration (int *ptr)
• Address operator (&) and indirection operator (*)

Relationship Between Pointers and Arrays

• How array names are treated as pointers
• Array element access through pointer arithmetic

Dynamic Memory Allocation

• Memory allocation with malloc function
• Memory release with free function
• Preventing memory leaks

Efficient Learning Tips

Because pointers are abstract concepts, visual understanding is important. The following approaches are effective.

Progressive Approach Starting from Small Programs

Begin with simple variable pointers, gradually expanding to arrays and structures. Rather than attempting complex code at once, perform detailed operation confirmations.

Early Mastery of Debugger Usage

Visualize memory states using GDB (GNU Debugger). Setting breakpoints and checking variable values one by one enables concrete pointer operation understanding.

Error Message Reading and Response Methods

Understanding “Segmentation fault” cause patterns and not ignoring compiler warning messages is important. Error messages become important clues for problem-solving.

Utilizing Code Reviews and Technical Communities

Reading others’ code on GitHub and Stack Overflow, asking questions about doubts, and receiving feedback deepens understanding.

Step 4: Practical Exercises and Projects

After mastering basics, solidify skills by tackling practical challenges.

Practical Learning Methods

Utilizing Competitive Programming

• AtCoder: Abundant beginner-friendly algorithm problems
• paiza: Challenge practical problems posed by companies

Solving problems on these platforms simultaneously improves both algorithm skills and C language implementation abilities.

Contributing to Open Source Projects

Read and understand C language projects published on GitHub. Starting with small bug fixes and feature additions enables learning actual development site coding conventions and best practices.

Creating Simple Embedded Systems

Through electronic work using microcontroller boards like Arduino, gain practical experience acquiring sensor data and controlling LEDs. This becomes a valuable opportunity to understand hardware-software interfaces.

Portfolio Construction Points

Create portfolios visualizing learning outcomes and usable in job-hunting activities.

Recommended Project Examples

• Simple command-line tools (e.g., file search tools, text processing tools)
• Simple data structure implementations (stacks, queues, linked lists)
• Embedded system examples (temperature sensor control with Arduino, etc.)

Publishing and Explaining Results

Uploading these results to GitHub and explaining design philosophy and innovations in README.md enables appealing technical abilities. Not just code quality, but documentation creation ability also becomes an evaluation target.

■Related Reading

Navigate the complete process of obtaining work visas in Japan as an IT engineer, covering application procedures, requirements, and expert tips for success.

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9．What is the C Language? A Language Effective for Long-Term Career Building

The C language has continued supporting system development foundations for half a century since its 1972 birth.

An indispensable presence across diverse fields including OS, embedded, IoT, and AI foundations, it maintains top TIOBE Index class and has high demand in domestic markets.

While learning difficulty is high, deep programming fundamental understanding is gained, with other language application abilities also acquired.

By utilizing public resources and learning progressively, careers as high-market-value engineers can be built.