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49 lines
2.3 KiB
Markdown
49 lines
2.3 KiB
Markdown
### main() Function
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* The main() function is the starting point of the program: `int main (int argc, char *argv[])`
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* The return type of the main() function is an integer (type int) and it is known as the `return value` of the program.
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* As a rule of thumb, `value 0 means success while non-zero means an error conditions.`
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---
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## Include Files
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* The purpose of these files is to tell the compiler about the existence of external functions which the source code will make use of.
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---
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## Preprocessor directives:
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| Directive | Description |
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|-----------------------------|----------------------------------------------------|
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| `#include "mine.h"` | Search current working directory first. |
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| `#include <stdio.h>` | Search command line directory, then the system. |
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| `#define TRUE 1` | Macro substitution, usually use capitals. |
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| `#define min(a,b)` | Macro substitution with parameters. |
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| `#define abs(a)` | Macro substitution. |
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| `#define note /* comment */` | This comment gets inserted every time `note` appears. |
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| `backslash \ at end of a line` | Means continue the line. |
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| `#undef TRUE` | Undefines a previously defined macro name. |
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| `#error` | Stop compiling at this point. |
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| `#if expression` | Conditional compilation, starts an `if` structure. |
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| `#elif expression` | Else if expression != 0, compile the following code. |
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| `#else` | Else, compile the following code. |
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| `#endif` | End of conditional compiling. |
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| `#ifdef macroname` | Like `#if`, compiles if `macroname` is defined. |
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| `#ifndef macroname` | Like `#if`, compiles if `macroname` is undefined. |
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| `#line number [filename]` | Set the origin for `__LINE__` and `__FILE__`. |
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| `#pragma` | Gives the compiler commands. |
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---
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## Create and execute a program
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In Linux systems:
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1. Open up a terminal (Ctrl + Alt + T)
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2. Create the program: nano nameProgram.c
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3. Write the program and save it
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4. gcc -o nameExecutable nameProgram.c (eg: gcc -o nameProgram_output nameProgram.c) |