Category:C: Difference between revisions

C
This programming language may be used to instruct a computer to perform a task.

Execution method:	Compiled (machine code)
Garbage collected:	No
Parameter passing methods:	By value
Type safety:	Unsafe
Type strength:	Weak
Type compatibility:	Nominative
Type expression:	Explicit
Type checking:	Static
Lang tag(s):	c
See Also:	C on the HOPL BNF Grammar for C C compared to other languages

Listed below are all of the tasks on Rosetta Code which have been solved using C.

C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the UNIX operating system. C evolved from its predecessor, B.

C has since spread to many other platforms, and is now one of the most widely used programming languages. C has also greatly influenced many other popular languages, such as C++ and Objective-C, which were originally designed as enhancements to C. People are so familiar with its syntax that many other languages such as AWK, PHP, Java, JavaScript, D, and C# deliberately used its "look and feel". C is the most commonly used programming language for writing system software, though it is also widely used for writing applications. C is the lingua franca of the open source community.

Versions

• K&R C was the first widely-used form of C. It was originally documented in The C Programming Language, published in 1978. It is named for the authors, Brian Kernighan and Dennis Ritchie (also the language's creator). Code in this style is virtually nonexistent today.
• C89 (often called ANSI C) is the version of C standardized by ANSI in 1989. It is the most commonly used and supported version of the language.
• C90 (often called ISO C) is identical to C89, republished by ISO in 1990.
• C99 is a significant improvement, adopting many features of C++ and standardizing common compiler extensions. It was standardized by ISO in 1999, and by ANSI in 2000. It is primarily supported by commercial C compilers, but most of its features are available in Clang GCC. [1]
• C11 is the previous standard, published in December 2011. It is the default for GCC as of version 5.1.
• C18 is the current standard, published in June 2018. It is the default for GCC as of version 8.1.
• C2x is the upcoming standard, planned for a 2021 publication. GCC 9 and Clang 9 have preliminary support for it.

Overview

Curly Braces

C uses curly braces as a separator for sections of code. All curly braces must be "balanced," i.e. every left curly brace must have a right curly brace after it. Most code writing programs will do this for you automatically. <lang C>int main() {

// your main program goes here

}</lang>

Scope

Unlike assembly which lets you jump anywhere or read any memory address, C imposes restrictions on labeled values. A variable defined inside a function can only be "seen" by that function, and not the ones outside it. Furthermore, you can re-use variable names inside a function and it refers to a different entity than the variable of the same name defined outside.

Functions

A function is made up of three parts: its return value, its name, and its arguments. <lang C>int main(void){ //This is the function "main," which takes no arguments and returns a 32-bit signed integer value. int sum(int a,int b){ //This is the function "sum," which takes two integer arguments and returns an integer.</lang> Note that the variable names listed as arguments when declaring a function are just for convenience. They need not be declared nor defined, nor do they refer to any variables in your program that happen to have the same name. It's only when a function is actually used are the argument variables required to exist. <lang C>int foo(int x){ return x; } // the "x" here is just a placeholder for whatever actually goes in when you invoke foo.

int main() {

int y; int z = 2;

y = foo(z); //note that x was never involved. That's because the "x" earlier was just a placeholder name.

}</lang>

Assignment

C allows you to define a variable as equal to a value, in more ways than just simple numerals. <lang C>int a = 3; //declare the variable a of type int, define it equal to decimal 3.

int b = -1; //declare the variable b of type int, define it equal to -1 (0xFFFFFFFF in hex)

char letter = "A"; //declare the variable "letter" of type char, it equals capital A. //C allows you to treat an ascii value as a numeral whenever you feel like it. Other languages do not.

char myString = "Hello"; //define the array "myString" containing the letters "Hello" followed by a null terminator.

int myArray[5] = {10,20,30,40,50}; //declare the array variable "myArray" containing integer values, with a maximum size of 5 elements. //Then assign 10 to the beginning, 20 after it, 30 after that, and so on.

int c = sum(a,b); //declare the integer variable "c". //Define it to equal the output of the function sum using the previously defined variables "a" and "b" as arguments. //This is only valid if the return type of the function "sum" matches the type of the variable "c."</lang>

Citation

• Wikipedia:C (programming language)