Program shape
A C program starts in main. Include stdio.h when using printf, and return a status code from main.
#include <stdio.h>
int main(void)
{
printf("Hello, C!\n");
return 0;
}What you will learn
- Write, compile, and run clear C programs using the standard library.
- Control program flow with decisions, loops, functions, and arrays.
- Use pointers and dynamic memory with explicit ownership and cleanup.
- Build practical programs that read input, process data, and report errors.
Practice method: type each example into Open Editor, predict its output, run it, then alter one input or condition and run it again.
1. Core language basics
Values and flow
Choose a type that describes the value, initialize variables, and make conditions easy to read.
for (int number = 1; number <= 5; ++number)
{
if (number % 2 == 0)
{
printf("%d is even\n", number);
}
}2. Functions and arrays
One function, one job
Functions make a program testable and reduce repeated logic. Give every function a declaration with clear parameter and return types.
int square(int value)
{
return value * value;
}Array bounds matter
C does not check array bounds automatically. Track the length and never index outside the valid range.
int scores[] = {72, 95, 81};
size_t count = sizeof scores / sizeof scores[0];3. Pointers and memory
A pointer holds an address. Dynamic memory from malloc must be checked and released exactly once with free.
int *score = malloc(sizeof *score);
if (score != NULL)
{
*score = 100;
free(score);
}Memory rule: initialize pointers, check allocation results, keep ownership obvious, and set freed pointers to NULL when they remain in scope.
Before you move on
- I can explain the structure of a C program.
- I can use loops and functions to avoid repetition.
- I know the difference between an array and a pointer.
- I check every dynamic allocation before use.
- I free memory I allocate.
- I can read compiler warnings and fix the first one.