C Standard Library Overview
A comprehensive overview of all C standard library headers. Learn what each header provides, when to use them, and how they work together.
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What You Will Learn
- ✓Know all major C standard library headers
- ✓Understand what each header provides
- ✓Choose the right header for your task
- ✓Understand library function categories
01The C Standard Library
The C Standard Library (also called libc) is a collection of header files that provide essential functionality for C programs. Instead of writing everything from scratch, you can use these pre-built, tested, and optimized functions.
Key Point: Header files contain declarations(function prototypes, macros, types). The actual function code is in a pre-compiled library that gets linked when you compile your program.
02Major Header Categories
<stdio.h>- Standard I/OInput/output operations - printf, scanf, file handling
<stdlib.h>- Standard LibraryMemory allocation, conversions, random numbers, sorting
<string.h>- String HandlingString manipulation and memory operations
<math.h>- MathematicsMathematical functions - trigonometry, logarithms, power
<ctype.h>- Character TypesCharacter classification and conversion
<time.h>- Date & TimeTime and date manipulation, formatting
<stdbool.h>- Boolean TypeBoolean type support (C99+)
<stdint.h>- Integer TypesFixed-width integer types (C99+)
03Complete Header Reference
| Header | Purpose | Version |
|---|---|---|
| <stdio.h> | Input/output operations | C89 |
| <stdlib.h> | General utilities (memory, conversion, random) | C89 |
| <string.h> | String and memory operations | C89 |
| <math.h> | Mathematical functions | C89 |
| <ctype.h> | Character classification | C89 |
| <time.h> | Date and time handling | C89 |
| <limits.h> | Integer type limits (INT_MAX, etc.) | C89 |
| <float.h> | Floating-point type limits | C89 |
| <errno.h> | Error handling | C89 |
| <assert.h> | Debugging assertions | C89 |
| <stddef.h> | Standard type definitions (NULL, size_t) | C89 |
| <signal.h> | Signal handling | C89 |
| <stdbool.h> | Boolean type | C99 |
| <stdint.h> | Fixed-width integer types | C99 |
| <inttypes.h> | Integer format conversion | C99 |
| <complex.h> | Complex number arithmetic | C99 |
| <threads.h> | Threading support | C11 |
| <stdatomic.h> | Atomic operations | C11 |
04How to Use Standard Libraries
1. Include the header
#include <stdio.h>2. Use the functions
printf("Hello!\\n");3. Link the library (automatic for standard libs)
gcc program.c -o programException: math.h requires -lm flag
05Summary
The C Standard Library provides:
- * I/O operations (stdio.h)
- * Memory management (stdlib.h)
- * String handling (string.h)
- * Math functions (math.h)
- * Time and date (time.h)
- * Type definitions and limits
- * Error handling and debugging
Test Your Knowledge
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