A header file in C, designated by a .h extension, contains function declarations and macro definitions and is included in source files using '#include'. This inclusion enables the compiler to understand the functions used, such as 'puts()', which is essential for managing arguments and return values. Without the header, the compiler would not recognize the functions, leading to compilation errors.

1. What’s a header? What’s a source-code file? Discuss the purpose of each.
Solution
The word Source File and Header is just a convention in C language. A header file is a file with
extension .h which contains C function declarations and macro definitions. These come either
with the compiler or are written by the programmers. The header files are always included into a
Source file by using '#include'. The preprocessor literally just copy and pastes the contents from
the header files into the source file, before the compilation begins.
Consider the below example for your reference:
#include<stdio.h>
int main(void)
{
puts("Hello World!");
return 0;
}
Without the header, the compiler doesnot know how to deal with the function "puts()". The
header lets the compiler know how to manage the arguments and return value. The function
puts() is a part of the library and to use its functioning, it has been included in the source code
file.