2.1 First C Program

1. 2.1 First C Program

2. First Program • Open visual studio, click new file • Save as “programName.c” • Program must start with letter and have no spaces • Must end with .c (visual studio will autoset .c if you select file type • There can be no spaces in the name!!!!

3. Header files • At the top of any program, you must include “header files” • These files are subprograms that tell the computer how to use built in features of the language. • Ex: <stdio.h>, <math.h>, <string.h>

4. First Program • First type in header files

5. Main Function • Ever Program in C has something called a main function • Basically tells the computer where to start executing code. • Goes after the header files

6. Intmain(void) • int main(void) • Int we’ll talk about later • Main tells computer this is where to start • Void tells computer not to expect any inputs at very beginning.

7. Int main(void)

8. Curly Brace • Whenever we want to enclose chunks of code, we always put the curly brace around them. • In this case, we want to section off the main chuck of code.

9. Main • Inside the main function we start writing the instructions for the computer • Computer executes code one after the other in order

10. Printf() • Printf() is a built in feature of C that was activated when we included stdio.h into the code • Its function is to print things to the screen

11. Printf()

12. Printf() • Double quote “hello” • Quotes needed because we just want to print whatever is inside, no special operations or variables

13. ; • Ever separate execeuted line in C needs to be ended with semi colon • If you forget semi colon the program DOESN’T WORK • Imagine a program with 500 lines of code and you forget one semi color…..= frustrating

14. Return 0;

15. return 0; • Most chucks of code, from now on will be called Functions usually return some type of value. • In our simple program, were not creating a special value so we will return 0 which in computer language is a sign of successful execution.

16. First Program • Click Save • Open VS Command Prompt • Navigate using “cd” to folder that holds your .c file • Type “cl firstProgram.c” +Entr • Type “firstProgram”+Entr • Viola

17. Compiler • Source code -> Machine Code • Needs to recompile after every change in program • Input .c file -> output .exe file

18. Program Documentation and Formatting

19. Formatting • All functions are indented from their start • Documentation is usually parallel to each other • Separate header files, different functions, variables, and other types of code.

20. Documenting • Required for full marks and in real world • Helps reader/programmer understand code • Two ways to document code • /* ……… */ is one way that omits everything inside slashes from compiler • // omits everything on that line from compiler

21. Things to Remember • Always include ; when needed • Always document • Always save as .c file • Keep track of opening and closing brackets • Formatting/Documenting makes things much easier to debug

22. Assignment • Create another program (brand new not just last program copy and pasted) that says “I am now a programmer” but this time try to : • return 1 • Forget ; • Forget to close bracket • Forget header file • Spell printf wrong • Forget to include closing */

23. Reading • Pg 26-28 for further description of initial C code