title:Undefined C
keywords:c,linux,asm
# Undefined C
There is possible to run piece of code inside online c compiler like https://www.onlinegdb.com/online_c_compiler
Or run locally. With base check is done with gcc compiler. There are many small tricks around running C code
in practice that aren't covered in any generic tutorials, so here is list of topics that may arise while
coding real C code outside of tutorials. For each case there is just small example, each of those could
take whole chapter on its own.
## Compile
__hello_world.c__
```c
int main() {
printf("Hello world\n");
}
```
```bash
gcc hello_world.c -o hello_world
gcc -m32 hello_world.c -o hello_world_32 #for 32bit target
```
## Syntax
### Variables
Standard list of available types
#### Check type size
All types have size that are declared in bytes. Some of the types are machine dependents.
like int/long, if there is needed machine independent types then there are int32_t/uint32_t/int64_t/uint64_t
Each architecture 8bi
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