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Reference C Programming Keywords

C KeyWords and Tutorial Index for John McGuinn ' C ' tutorial

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Command

Use

Description/comment

Example

  
--     a --  
! Operator NOT if !(a == 0);  
!= Operator NOT Equal to    
#define   Define a CONSTANT #define PI 3.1415927  
#include   Add the contents of an include file
<> denotes file in a known library folder.
"" denotes file
#include <stdio.h>
#include "tms.h"		  
^   bitwise exclusive or. result 1 if either bit is 1 only    
&   bitwise and.  result 1 if both bits 1    
&& Operator && operator  (and)    
|   bitwise or.  result 1 if either bit is 1 or both bits 1    
|| Operator || operator     (or)    
% Operator Modulo Division remainder = b % c remainder=7%2      ans  1  
%+4d Format Forces the sign + or – to be displayed Use below in printf & scanf  
% d Format Prints a space in place of + sign    
%*d Format As above using a variable printf("N=% d", Fortnum, age);  
%*.*f Format As above using 2 variables    
%+4d Format Forces the sign + or – to be displayed    
%04d Format Pad with leading zeros    
%4d Format Format to 4 chars.    
%-4d Format Left justify    
%5.3f Format Format to 5 chars for full num, 3 decimal places cprintf("The average is %5.4f",average);  
%-5.3f Format As above but LEFT justified    
%c Format Character    
%d    Format Integer    
%f Format Floating point / Double    
%G Format Force a Decimal point    
%ld Format Long Integer    
%p Format Hexadecimal    
%s Format String    
%ud Format Unsigned Integer    
&& Operator AND make left most likely false if (gender == 1 && age >= 65)  
* Operator      
/   Divide, no remainder when used on integers 7/3     answers 2  
/*    */   Comments that can be spread of several lines if required. /* Comments  */  
//   Comment. Older compilers may not support this // Comments to end of line.  
;        
{ }   Marks the start and end of a section of code for a function.   T2 { }
(    )   Follows functions, & holds parameters cprintf ("Hello" ); T2 ( )
[    ]        
\307C   Displays ° C    
\' format single quote    
\" format double quote    
\\ format backslash    
\0 format Null Char.    
\a format alert(bell)    
\b format backspace    
\f format formfeed      Cursor to next logical Page    
\n format newline cursor down 1 line Often used with \r in a string
\n\r 		T2 \n
\r format return Beginning of current line Often used with \nin a string
\n\r 		T2 \r
\t format horizontal tab    
\v format vertical tab    
     
|| Operator OR  make left most likely to be true    
+ Operator      
++ Operator   i++          ++i Tut 3 Shortcut
-- Operator   i--             --i
< Operator      
<= Operator      
= Assign  N.B. Logic error if confused with == num = 7; 7 is assigned into variable num Tut 3
== Operator Equal to if(a == b);  
> Operator      
>= Operator      
+=
 Operator   num += 3 Tut 3 Shortcut
-=
 Operator   num -= 3
*=
 Operator   num *= 3
/=
 Operator   num /= 3
%=
 Operator   num %= 3
         

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ARRAYS   Declare array with 8 elements, 0-7 Assign 2 into sixth element    6 rows    9 cols     Initialises the 1st element to 0, & the remaining elements by default to 0 Use symbolic constants to define the number of elements in an array See char for strings int num[ 8] ; num[ 5]=2 ; int TwoDimentionArray [ 6] [ 9] ; int n[  ] = { 32, 10, 5,14 }; int n[ 10] = {0} ;   # define SIZE 10 int n[SIZE] ;        
atof <math.h>  <stdlib.h> Converts a string to floating point, or 0 if cant convert f = atof(str) ;
atoi <math.h>  <stdlib.h> Converts a string to integer, or 0 if cant convert i = atoi(str) ;
break Keyword use within   while   do   for   switch if ( n == 5) break ;

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case   See switch    
ceil, ceill <math.h>  Round up       See floor  up=ceil(num); up=ceill(num);  
cgets        
casts   floatVariable=(float) intVariable * 2.3    
char Data type Keyword can be displaced as a letter or number pointer to a variable Array declaration str_s [ c], pointer to a variable printf("ASCII value of %c is %d", letter, letter) ; char letter='A' ; char *String="Some Name" char name[  ]="John" char *n [  ]={{ "item1"},                       { "item2"},                       { "etc.    "}} ; char menu[]="a. first\r\n"                    ="b. second\r\n"                     ="9. ninth\r\n"; cprintf (menu);  
clearerr <conio.h>      
clrscr() ; <conio.h>     T2 clrscr() r30
const Keyword Define a Constant const yr_now = 1996 ;  
continue   Misses the rest of the code in a loop cycle    
cprintf() <conio.h> function that displays a formatted string on to the screen. Not in ANSI, used by T223 students. cprintf( "Hello World" ) ;
cprintf( "Number=%i ", num1) ;		 Tut 2 cprintf()

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declaration   Declaration See   int  float char   
default      
define   define CONSTANTS #define PI 3.1415927
delay(); <dos.h> Delay in millisecs. delay(1000) ;         // 1 second delay
do … while Keyword Loop   while (++ counter <=10) ; do {          statement(s) ; }     while (condition);
double float Keyword Data type double float lge_num1, lge_num2;
continue      
else Keyword see:  if see Tut 5
eof   is a negative num, usually -1 usually Ctrl + z on a PC ( system dependant)  
  <stdlib.h> exit(0)  ok   exit(1)  error  

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getch <conio.h> No echo,   c = getch() ; switch(getch() ) { ….. }
getchar <studio.h> Gets a Char, echo to screen, wait for Carriage Return.  On end of File or error returns EOF while((c = getchar()) != '\n')
getche <conio.h> Gets Char, screen echo c = getche() ;
gets <studio.h> Gets a string. Declare: char string[ 80] gets(string) ;
gotoxy <conio.h> Not Win32s or Win32 GUI gotoxy( col, row ) ;
if( )
 Keyword if ((x < y)  && (x > 0)) 
if (count < 50) count++;
if (( x < y ) && x > 0 ))
       { 
       doSomething ;
      }
Tut 6
if( ) … else   Note in the example where the semi colon is NOT used 
if ( x < y )
      {    
			    printf ("y is larger") ;
      } 
else
      {
       printf ("x is larger") ;
      }
int Keyword Data type Range (varies) –32,768 to +32,767 unsigned o to 65,535 Array declaration num [ x ] int num, age, num2; unsigned int num;
isalnum( c ) <ctype.h> Returns True if c is a letter or digit if(isalnum( c ))
isalpha( c ) <ctype.h>      letter  
isascii( c ) <ctype.h>     ASCII between 0­­ – 127  
iscntrl( c ) <ctype.h>     delete char, or ordinary control char  
isdigit( c ) <ctype.h>     Digit.   Read chars until nondigit is input for (I=0; isdigit( c ) ; c=getchar() )
islower( c ) <ctype.h>     lowercase letter  
isprint( c ) <ctype.h>     printing char including space  
ispunct( c ) <ctype.h>     punctuation char  
isspace( c ) <ctype.h>     space, tab, vert tab, line or form feed, CR        // skipover leading whitespace while (isspace(c=getchar()) ) ;
isupper( c ) <ctype.h>     uppercase letter    

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kbhit      
long Keyword Data type unsigned  0 to +4,294,967,295 long num, age, num2; unsigned long num;
main(  )   Requires {      } T2 main()
modf   Returns remainder, stores integer part in *ipart    see fmod  
pow <math.h> Raise to the power of n = pow(2.4 , 3) ;   // power of 3
printf() <stdio.h> Displays info on the screen, may include text &/or variables .
T223 students use cprintf() in place of printf()		 printf("Hello World in %d", thisYear);
putchar <stdio.h> Display the value in variable putchar(letter);
rand <stdlib.h> Produces a number in range: 0-32767(min of)                                                0-5                                                1-6 Produces same set of numbers. See: srand(seed) i = rand( ) ; i = rand( )  % 6 ; i = (rand( ) % 6) + 1 ;
RAND_MAX   Symbolic constant to holding max. rand range e.g. 32767 or more, system dependent
return     return(avalue)

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scanf() <stdio.h> Reads data entered at the keyboard, and assigns it to a variable Must start with literal string. Note & address operator scanf("%d", &number); scanf("%d %d", num1,num2);
short Keyword Data type short num, age, num2;
sprintf      
srand <stdlib.h>
<time.h> 		Proceed rand to seed the rand srand(time(NULL)) ;  // super seeding srand(seed) ; // seed is unsigned integer
sscanf      
str xxx      Check with your compiler upper / lower case differences  
strcat <string.h> string concatenation              Page T421 strcat (str1, str2) ;
strcmp <string.h> compare returns 0 if=, 1 if s1 is > s2,                                      2 if s1 is < s2 i = strcmp(s1, s2) ;
strcpy <string.h> Copy                                     Page T419 strcpy (strDest, strSource) ;
strlen <string.h> String Length iLength = strlen(str) ;
strncat <string.h> string concatenation              Page T423 strncat (str1, str2, num) ;
strncmp <string.h>   i = strncmp(s1, s2, num) ;
struct      
switch <stdio.h> without the break all statements, including later case statements, after the first match are processed case 'd' : case 'D' : case '\n' : case ' '  : break //ignores newline & spaces Tut 6
switch ( switch variable ) 
{case constantExpression : statement; [break;]
      .

      default : statement;
}

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tolower(c) <ctype.h> See also  lowercase() string[ i ] = tolower(string[ i ]) ;
toupper(c) <ctype.h>    
typedef Keyword Used to create new names for existing variables and function types  
unsigned Keyword Data type will contain only positive values See int  long unsigned short num, age, num2;
void      
wherew()     goto(2,wherey()+3)
while Loop See also do ... while count = 0; while( ++ count <= 5) ;  // 5 repetitions 
while (condition)
    {    
     statements ; 
    }

 

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