Compiling one source file into one executable file:
gcc prog-1.c -o prog-1.exe

Running the executable file:
./prog-1.exe

Compiling two or more source files into one executable file:
1) gcc prog-1a.c prog-1b.c -o prog-1.exe

OR

2)
gcc -c prog-1a.c
gcc -c prog-1b.c
gcc prog-1a.o prog-1b.o -o prog-1.exe