History and Features of C

Origin of C

C was developed by Dennis Ritchie at Bell Labs between 1969 and 1973. It grew out of the B language (itself derived from BCPL) and was first used to rewrite the UNIX operating system.

Timeline:

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Why Learn C?

• C is a middle-level language — it has features of both high-level and low-level languages.
• It is the foundation of many modern languages (C++, Java, Python runtime is in C).
• Used in operating systems, embedded systems, compilers, and more.

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Features of C

1. Simple — easy to learn with a small set of keywords (32 in C89).
2. Portable — programs can run on different hardware with minimal changes.
3. Fast — compiled language with direct memory access.
4. Structured — supports functions and modular programming.
5. Rich Library — vast standard library for I/O, string handling, math.
6. Pointers — direct memory manipulation via pointers.
7. Extensible — you can add your own functions to the library.

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Structure of a C Program

/* Documentation Section */
#include <stdio.h>       /* Preprocessor Directive */

int main() {             /* Main Function */
    printf("Hello, World!\n");
    return 0;
}

Sections of a C program:

• Documentation — comments explaining the program
• Preprocessor directives — #include, #define
• Global declarations — variables/functions accessible everywhere
• main() — entry point of every C program
• User-defined functions — additional functions

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Compilation Process

1. Source Code (.c file) → Preprocessor → Expanded Source
2. Expanded Source → Compiler → Assembly Code
3. Assembly Code → Assembler → Object Code (.obj)
4. Object Code + Libraries → Linker → Executable (.exe)