Stdio.h

1. Standard Input/Output

Functions for console input and output operations.

Function	Description	Example
int printf(const char *format, ...)	Print formatted data to standard output (stdout).	printf("Age: %d", 25); // Output: Age: 25
int scanf(const char *format, ...)	Read formatted input from standard input (stdin).	scanf("%d", &age); // Reads integer into variable age
int putchar(int char)	Write a character to standard output.	putchar('A'); // Output: A
int getchar(void)	Read a character from standard input.	char c = getchar(); // Waits for user input

2. File Operations

Functions to open, close, and manipulate files.

Function	Description	Example
FILE *fopen(const char *filename, const char *mode)	Open a file. Modes include "r" (read), "w" (write), "a" (append).	FILE *fp = fopen("data.txt", "r"); // Opens file for reading
int fclose(FILE *stream)	Close an open file stream.	fclose(fp); // Closes the file pointer fp
int fprintf(FILE *stream, const char *format, ...)	Write formatted output to a specific file stream.	fprintf(fp, "ID: %d", 42); // Writes "ID: 42" to file
char *fgets(char *str, int n, FILE *stream)	Read a string (line) from a file stream.	fgets(buff, 100, fp); // Reads a line into buff

3. String Formatting

Functions for formatting data into strings or parsing data from strings.

Function	Description	Example
int sprintf(char *str, const char *format, ...)	Write formatted data to a string buffer instead of stdout.	sprintf(buf, "Hi %s", "Bob"); // buf becomes "Hi Bob"
int sscanf(const char *str, const char *format, ...)	Read formatted data from a string.	sscanf("Year 2025", "%*s %d", &y); // Parses 2025 into variable y