|
| |
Introduction
 | Developed in the early 70's by Dennis Ritchie at Bell Labs |
| Standard established in 1978 by Ritchie and Dennis Kernighan |
| C is considered a highly portable language because of it's simplicity. |
| C is a relatively small language with few hardware-specific elements. |
| Input/output and memory management are handled via C library-based
functions. |
| Machine code generated in C is considered highly efficient. |
| Some consider the language to be a high-level assembly (but it is not
assembly) because of it's terseness. |
| C compilers have been developed for Unix, Linux, DOS, Windows, mainframes,
and many other platforms. |
Language Fundamentals
Program Structure and Organization
/*
Simple hello world program.
by Dave Hillman
*/ |
Comments and program file header |
#include <stdio.h>
|
Pre-Processor Directives |
main(void)
{
printf("Hello World \n"); /* output something to the screen */
printf("\n\tPress any key to end program."); /* let the user know how to
end the program */
getchar(); /* look for input from the keyboard */
return 0; /* return control to the OS */
}
|
Main function - starting point for the program
May be placed anywhere in a source file. |
void otherfun(void)
{
....}
|
Other functions |
| Language/character sets: C has two character sets:
- Source character - what the program is written in.
- Execution character - character set for delivery.
 | Each contains a basic 26 upper and 26 lower alphabet characters, ten
digits, 29 graphic characters, and 5 white space characters (space, tab,
etc.). |
| Also null character, \0 and escape control characters: e.g., \n
- new line |
|
| Identifiers and keywords:
| Function, variable, etc. contain letters, digits, and underscore. |
| First character cannot be a digit. |
| Are case sensitive. |
| No restrictions on length, only first 31 characters are usually
significant. |
|
| Source code management (files, etc.)
| Source files have .c extension |
| Header files have .h extension, |
|
| Program delivery:
| C programs are compiled. |
| Various intermediate files are created:
 | Source |
| Stripped source (comments, etc.0 |
| Object |
| Compiled executable. |
|
| Programs are limited to operating systems they are compiled for. |
| Commercial compilers include:
|
|
Data Types
| Basic data types:
| char - character |
| int - an integer, in the range -32,767 to 32,767 |
| long int - larger integer (up to +-2,147,483,647) |
| float - floating-point number |
| double - floating-point number, with more precision and greater
range than float |
|
| Does not have an explicit Boolean |
| Characters and arrays of characters (strings) are represented with single
or double quoting. |
| Declaring variables:
| int i; - initializes a variable of type integer called i |
| int i = 3; - initializes and i and sets it equal to 3 |
| int i1, i2; - initializes two variables: i1, and i2 |
|
| Variables are case sensitive. |
| Arrays:
| All data types support array declarations. |
| Example: char line[81]; - declares a character array with 81
positions |
| Filling an array: line[2] = 'A' |
| Multidimensional arrays are possible: e.g., short
array_name[50][20][10] creates an array with 10,000 elements. |
|
| Variable scope:
| Variables declared in functions live within the function. |
| static int i; - creates a variable scoped within the file. |
| extern int i; - creates a variable scoped within an application. |
|
Expressions and Operators
| Math operators (in order of precedence)
| * multiplication |
| / division |
| % modulus (remainder) |
| + addition |
| - subtraction |
| +x value of x |
| -x negative value |
| ++ increment |
| -- decrement |
|
| Assignment operator: = |
| Relational operators
| <, <=, >, >= |
| == is equal to |
| != is not equal to |
|
| Logical operators
| && - logical and |
| || - logical or |
| ! - logical not |
|
| Other operators:
| () - function call, e.g., pow(x,y) |
| (type) - cast, e.g., (long)x - the value of x is set with type long |
| sizeof - size in bytes |
| ?: - conditional evaluation |
| , - sequence operator |
|
Control Statements
| If-then
|
if (expression) {
statement;
statement;
.... }
if (expression) {
statement;
statement; }
else
statement;
if (expression) {
statement;
statement; }
else {
statement;
statement; }
if (expression) {
statement;
statement; }
else if (expression)
statement;
C Libraries
C depends on a set of libraries (ANSI C Library) to handle a variety
of common and advanced functions, macros, and data types. The libraries
are based upon standard sets of tasks including:
| Standard Input/Output (stdio.h) |
| Math functions (math.h) |
| String handling functions (string.h) |
| Time and date functions (time.h) |
| Miscellaneous library functions (stdlib.h) |
These libraries are included in various C source files to provide the desired
support functions for a program.
Input/Output
Given the above and other libraries, C input/output is handled by a variety
of functions including some of the following (there are more than this):
| Standard Input and Output - C "assumes" that standard devices are
used for input (keyboard) and output (command line display) |
| Keyboard input
| scanf() - reads a standard input (from a keyboard) |
| gets() - reads a string from standard input |
|
| Screen output
| printf() - handles output to the screen |
|
| File I/O
| fopen() - opens a file for access, returns a handle for processing |
| fclose() - closes an open file |
| fgetc() - reads a character from a file |
| fgets() - reads a string from a file |
|
Resources
References
Tutorials
And just to prove I have a sense of humor, the following songs about C are
done to Beatles tunes:
http://www.indigo.org/humor/beatles.html (enjoy)!
|