Graph
Your first C program is one compile away. It is much less mysterious once it prints.
Display "Hello World!" followed by a newline
Display a single newline character on standard output
Write a program that outputs the letter 'e' followed by a newline
Display all digits in descending order on one line
void print_digits(void)
int putchar(int c)
Draw the frame of a rectangle whose width and height come from the arguments