C Program Structure:

1. Preprocessor Commands (hiền xử lý: #include, #define, #if, #ifdef, ....)
2. Functions (hàm, conn trỏ hàm, hàm inline, ...)
3. Variables (scope: global, local; type: char, int, float, double, void; class: auto, register, static,extern)
4. Statements (if, if ...else, elseif, switch, while, do, for loop) 
5. Expressions ( arithmetic, assignment, logical, bitwise, ...)
6. Comments (/* block comment */, //line comment)

 #include <stdio.h>  
 int main()  
 {  
   /* my first program in C */  
   printf("Hello, World! \n");  
   return 0;  
 }  

Compile and Execute

1. cd
2. gcc helloworld.c  (compile)
3. ./a.out  (execute)

hoặc

1. cd
2. gcc helloworld -o helloworld
3. ./helloworld 

Ký tự ./ chỉ ra thư mục hiện tại