What Is C Programming? History, Use Cases, and Standards Explained

In this tutorial, you will learn about What Is C Programming? History, Use Cases, and Standards Explained. We cover key concepts, practical examples, and best practices to help you master this topic.

C is a procedural systems programming language developed at Bell Labs in 1972 by Dennis Ritchie, designed for writing operating systems with direct memory access and minimal runtime overhead.

Why It Matters

C is the language that built everything -- Linux, Windows, Python, Git, and virtually every operating system kernel. Understanding C gives you insight into how computers actually work at the hardware level, making you a better programmer in every other language. Embedded systems, IoT devices, and game engines all rely on C for its unmatched performance and predictability.

Real-World Use

The Linux kernel, which runs on 90 percent of the world's servers and all Android devices, is written almost entirely in C. Embedded systems in cars, medical devices, and smart appliances use C for real-time control. The Python interpreter and the Redis database are both implemented in C. At DodaTech, C programming powers the core scanning engine of Durga Antivirus Pro for maximum performance and low-level file system access.

What You Will Learn

• The history and evolution of C from K and R through C23
• Systems programming and where C excels
• Key differences between ANSI C, C99, C11, C17, and C23 standards
• Real-world applications and ecosystems built with C
• Why C remains relevant after 50 years

Learning Path

flowchart LR
  A[What Is C
You are here] --> B[Installing Compiler]
  B --> C[Hello World]
  C --> D[Fundamentals]
  D --> E[Pointers & Memory]
  style A fill:#f90,color:#fff

History of C

C was created at Bell Labs by Dennis Ritchie between 1969 and 1972. The name C came from its predecessor, the B language, which was itself derived from BCPL. C was developed alongside the Unix operating system -- in fact, Unix was rewritten in C in 1973, making it one of the first operating systems written in a high-level language rather than assembly.

Before C, system software was written in assembly language, which is specific to each processor architecture. C provided a portable abstraction layer: write once in C, compile for any architecture with a C compiler. This portability was revolutionary and made Unix the first portable operating system.

In 1978, Brian Kernighan and Dennis Ritchie published "The C Programming Language," known as the K and R book. This was the de facto standard for C until the American National Standards Institute (ANSI) standardized C in 1989, producing ANSI C (also called C89).

C Standards Evolution

Understanding C standards is important because code written for one standard may not compile under another. Each standard introduced new features while maintaining backward compatibility.

ANSI C / C89

The first formal standard, published in 1989. It introduced function prototypes, the void type, const and volatile qualifiers, and structure assignment. Most C code written before 1999 follows this standard.

C99

Published in 1999, this standard added:

• Inline functions with the inline keyword
• Declaring variables anywhere in a block (not just at the beginning)
• Designated initializers for structs and arrays
• Variable-length arrays (VLAs)
• The long long type for 64-bit integers
• Single-line comments with //
• Compound literals and flexible array members

C11

Published in 2011, this standard focused on safety and concurrency:

• The _Generic keyword for generic selections
• Anonymous structs and unions within structs
• Multithreading support with _Thread_local and the threads.h header
• Bounds-checking interfaces (annex K, optional)
• Static assertions with _Static_assert
• The noreturn specifier for functions that do not return

C17

A bug-fix release published in 2018. It addressed defects in C11 without adding new features. Most compilers that claim C11 support actually implement C17.

C23

The latest standard, published in 2024. It brings modern features to C:

• The bool, true, and false keywords as built-ins (no need for stdbool.h)
• nullptr and nullptr_t for type-safe null pointers
• constexpr for compile-time constant expressions
• Attributes using [[attribute]] syntax
• auto for type inference
• Decimal floating-point types
• Enhanced static_assert with no need for a message string argument

What Standard Should You Use?

For new projects, target C23 if your compiler supports it (GCC 13+, Clang 16+). For maximum portability, target C11 or C17. Embedded systems often use C99 or even C89 due to limited compiler support on older microcontrollers.

C vs C++: Key Differences

Many beginners confuse C and C++. While C++ started as "C with classes," they have diverged significantly:

The important insight: C is essentially a subset of C++ for most practical purposes, but C++ adds features that make it more complex. Learning C first gives you a solid foundation for understanding C++.

Where C Is Used Today

Despite being 50 years old, C remains one of the most widely used programming languages. Here is where it dominates:

Operating Systems

Linux (95 percent C), Windows kernel (mostly C), macOS kernel (C and C++), and all major BSD variants are written in C. The boot loaders, device drivers, and memory managers all use C.

Embedded Systems

Microcontrollers with limited RAM (kilobytes, not gigabytes) run C code. The Arduino platform uses C/C++. Automotive ECUs, medical pacemakers, and smart thermostat firmware are all written in C.

Compilers and Interpreters

The reference implementations of Python (CPython), Ruby (CRuby), PHP (Zend Engine), and Lua are all written in C. LLVM and GCC, the two most important compiler toolchains, are written in C and C++.

Databases

SQLite, the most widely deployed database engine, is written in C. Redis, the in-memory data store, is also C. The core of MySQL and PostgreSQL have substantial C components.

Game Development

Game engines like Unreal Engine and Godot use C++ for their core, but many retro and indie games use C directly. The popular raylib library is a C game development framework.

Security Tools

Durga Antivirus Pro uses C in its core scanning engine for maximum file system performance. Network security tools like Nmap and Wireshark are written in C.

Common Mistakes

1. Assuming C Is Only a Historical Language

Many developers think C is outdated. In reality, C is still the most widely used language for systems programming. New C23 features show active development.

2. Confusing C Standards

Code written for C89 may not compile as C11 due to removed features like gets(). Always specify your target standard with -std=c11 or similar compiler flags.

3. Thinking C and C++ Are the Same

Writing C code that compiles as C++ is possible but not guaranteed. C allows implicit type conversions that C++ rejects. Write C as C, not as "C with C++ tricks."

4. Ignoring the Preprocessor

The C preprocessor is powerful but dangerous. Overusing macros can make code unreadable. Use const and enum instead of #define for constants where possible.

5. Not Understanding Undefined Behavior

C's standard defines certain operations as "undefined behavior." The compiler can assume these never happen and optimize accordingly. Signed integer overflow, dereferencing NULL, and accessing array out of bounds are all undefined.

Practice Questions

1. What year was C created and by whom? C was created by Dennis Ritchie at Bell Labs between 1969 and 1972, first published in 1972.

2. What is the difference between C89 and C99? C99 added inline functions, designated initializers, variable-length arrays, long long type, and single-line comments.

3. Why was C important for Unix portability? Unix was rewritten in C in 1973, making it the first portable operating system that could run on different hardware architectures with a C compiler.

4. What does undefined behavior mean in C? The C standard does not define what happens. The program might crash, produce wrong results, or appear to work. Examples include signed integer overflow and buffer overruns.

5. Challenge: Research which C standard your current compiler defaults to and what new features are available in C23 that could benefit your projects.

Mini Project: Research and Compare

Write a simple C program that uses the C23 nullptr keyword (if your compiler supports it) and prints the size of nullptr_t:

#include <stdio.h>

int main() {
    int *ptr = nullptr;
    printf("Size of nullptr_t: %zu bytes\n", sizeof(nullptr_t));
    printf("Pointer value: %p\n", (void*)ptr);
    return 0;
}

If your compiler does not support C23 yet, use NULL instead and note the difference.

FAQ

What is Next

Proceed to Installing a C Compiler to set up GCC or Clang and write your first C program. After that, continue with Hello World in C to understand the compilation Process.