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131 lines
2.8 KiB
Markdown
131 lines
2.8 KiB
Markdown
---
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title: "08-intro-to-c"
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aliases:
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tags:
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- lecture
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- cosc204
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sr-due: 2022-08-17
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sr-interval: 9
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sr-ease: 250
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---
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Developed 1972 for Unix
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- widely used
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- compilers esxist for most OSs and architectiures
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- diverse use
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- OSs, device drivers, protocol stacks
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- less so for application software
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- low level
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- language features map to CPU features
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- not Object Oriented
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- no classes etc
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> “C is an imperative procedural language supporting structured programming, lexical variable scope, and recursion, with a static type system. It was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to machine instructions, all with minimal runtime support. Despite its low-level capabilities, the language was designed to encourage cross-platform programming. A standards-compliant C program written with portability in mind can be compiled for a wide variety of computer platforms and operating systems with few changes to its source code.” - wikipedia
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``` c
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#include <stdio.h>
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int main(int argc, const char *argv[])
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{
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puts("Hello World");
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return 0;
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}
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```
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# \#include
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java uses .class files, C uses .c and .h
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- .c for implementation
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- .h for extern declarations (similar to `public`)
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java uses `import`, C uses `#include`
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``` c
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#include <stdio.h>
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#include "myfile.h"
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```
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- `#include` literally includes the file with the given name right there into the file eing compiled
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- in `hello_world.c` we include `stdio.h` so we can call `puts()`
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# Routines
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``` c
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int main(int argc, const char *argv[])
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{
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}
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```
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routines can be scoped to just the source code file
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- `static int eleven(void`
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routines must be declared bfore being used
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- `extern int eleven(void):`
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# if, const, for, while, do, case etc same as java
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# Types
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```
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char
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float, double
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int, short, long
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signed, unsigned
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void
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```
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## sizeof
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- to find out size of any type (built-in or user defined)
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## stdint
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## Structs
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- like classes but without methods
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- all fields public
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- you can have structs in structs
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## typedef
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- any type can be given a new name using typedef
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```
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typedef struct
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{
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float x, y, z;
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} coordinate;
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```
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## static
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- the scope of this routine is local to this file
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- this variable maintains its value between calls
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```
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void keeper(void) {
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static uint64_t times_called = 0;
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times_called++;
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printf("Count:%llu\n", times_called);
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}
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```
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## typecasting
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like java
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```
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uint64_t y = 1024;
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unit32_t x = (unit32_t) y;
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```
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## Keywords to ignore
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- auto
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- all local variables are auto
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- register
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- deprecated
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## keywords to think about
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- volatile
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- do not optimize accesses to this variable
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- might be changed by another thread or a harware event
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- you're likely to see this in operating system souce code
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- you're likely to see this in multithreaded programs
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