why C is called a system programming language

C is called a system programming language because it was designed and is primarily used for writing system software, which includes operating systems, device drivers, and other low-level programs that interact directly with hardware. Here are several reasons why C is particularly suited for system programming:

1. Low-Level Access

• Direct Memory Access: C allows direct manipulation of memory using pointers. This is crucial for system-level programming where direct memory access is often required.
• Bit Manipulation: C provides operators for direct bit manipulation, essential for writing device drivers and interacting with hardware registers.

2. Efficiency and Performance

• Minimal Overhead: C code is compiled to efficient machine code with minimal runtime overhead, making it suitable for performance-critical applications.
• Fine-Grained Control: Programmers have fine-grained control over how resources (memory, CPU) are used, which is important for systems that need to be highly optimized.

3. Portability

• ANSI C Standard: The ANSI C standard ensures that C code can be compiled and run on different hardware and operating systems with minimal changes.
• Hardware Abstraction: While providing low-level access, C also allows for a degree of hardware abstraction, making it easier to write portable code.

4. Rich Set of Operators

• Comprehensive Set of Operators: C has a comprehensive set of operators (arithmetic, logical, bitwise, etc.) that enable efficient implementation of complex operations directly in code.

5. Compactness

• Small Runtime Library: The C standard library is relatively small compared to those of higher-level languages, which is advantageous for system programming where memory is at a premium.
• Modularity: C's support for modular programming (via functions and file-based separation) helps in managing large system software projects.

6. Legacy and Influence

• Historical Significance: Many of the first operating systems (including UNIX) and system-level software were written in C, setting a precedent for its use in system programming.
• Influence on Other Languages: Many modern system programming languages (like C++, Rust, and Go) are influenced by C and retain its core concepts, ensuring that knowledge of C is beneficial for understanding these languages.

7. Assembly Language Integration

• Inline Assembly: C allows the integration of assembly language within C code, enabling developers to perform highly optimized operations that are not possible in pure C.

Example: Writing a Simple Device Driver

A simple example illustrating why C is suited for system programming could be a minimal device driver code snippet:

#include <stdint.h>

#define DEVICE_REGISTER_ADDRESS 0x4000
#define DEVICE_REGISTER (*(volatile uint8_t *)DEVICE_REGISTER_ADDRESS)

void init_device() {
    // Set device register to a specific value
    DEVICE_REGISTER = 0x01;
}

void write_to_device(uint8_t value) {
    // Write value to device register
    DEVICE_REGISTER = value;
}

uint8_t read_from_device() {
    // Read value from device register
    return DEVICE_REGISTER;
}

In this example, the use of pointers and direct memory access is evident, showcasing the kind of low-level operations typically required in system programming.