Here is a list of some commonly used header files in C along with their full names and a brief description of their functionality: 1. `<stdio.h>` (Standard Input/Output):    - Full Name: Standard Input/Output Header    - Description: Contains functions for standard input and output operations, including `printf`, `scanf`, `fgets`, `fopen`, etc. 2. `<stdlib.h>` (Standard Library):    - Full Name: Standard Library Header    - Description: Provides general-purpose functions for memory allocation, type conversions, random number generation, sorting, etc. Includes functions like `malloc`, `free`, `atoi`, `qsort`, etc. 3. `<string.h>` (String Operations):    - Full Name: String Header    - Description: Contains functions for manipulating strings, including string copying, concatenation, comparison, searching, and tokenization. Includes functions like `strcpy`, `strcat`, `strcmp`, `strlen`, `strtok`, etc. 4. `<mat...