main() - The program begins executing at the beginning of main and there must be atleast one in the program.
"Hello, world" - a sequence of characters in double quotes is called a string constant or character string or string literal.
/*.....*/ - Multi-line comment.
The above sizes are machine-dependent.
Storing foating point number in int truncates it (i.e. strores only the integer part).
In the below code, % followed by character indicates where the arguments are to be substituted.
printf("%d \n", num); //integer
printf("%ld \n", num); //long integer
printf("%f \n", num); //float, double
printf("%c \n", fname); //char
printf("%s \n", fname); //string
printf("%o \n", num); //octal
printf("%x \n", num); //hexadecimal
printf("%% \n", num); //for % itself
printf("%d \n", num); // integer has 6 digits width
printf("%f \n", num); // integer has 6 digits width
printf("%6d \n", ); // integer has 6 digits width
printf("%.3f\n", ); // float can have any width integer part but decimal part has a limit of 3 digits
printf("%.0f\n", ); //supresses printing of the decimal point and the fractional part
printf("%3.2f\n", ); // atleast 3 wide, 2 after decimal point
The width in the integer part does not actually play a part as evident from below.
#include<stdio.h>
int main()
{
float n = 656.56789;
int m = 251;
printf("%2.3f\n", n);
printf("%2d\n", m);
printf("%.0f\n", n);
return 0;
}
Output: 656.568 //rounded off to only 3 decimal places
251 //no effect
657 //whole decimal part rounded off with no digit left after decimal
#define name replacement-text
#define LOWER 0
#define UPPER 300
#define STEP 20
// We can now proceed to use the above defined constants throughout the program as it is.
// They are written in uppercase to distinguish them from variables.
getchar() and putchar() - Standard library provides them to read/write just one character at a time.c = getchar(); //reads the next character from text stream and return its value
putchar(c); //prints a character each time it is called
End Of File (EOF) - EOF is just a symbolic constant stored in <stdio.h> with some integer value that we don’t need to know. Whenever a file ends it returns a value that cannot be confused with any character’s integer value, that value is EOF.
Precedence of != is higher than =.
Expressions can be evaluated inside the loop condition.
#include<stdio.h>
main(){
int c;
while((c = getchar()) != EOF) //getchar() call is perfectly fine here
putchar(c);
}
nl = nw = nc = 0;
//above expression is evaluated as follows
(nl = (nw = (nc = 0)));
int func(int n, int m); //Declaration
or
int func(int , int); //also valid
int func(int n, int m) //formal paramters (parameters)
{
//function statements
return expression; //zero implies normal termination, otherwise unusual or errorneous termination
}
main()
{
func(x,y); //actual parameters (arguments)
}
Functions are always CALLED BY VALUE in C. We can be assured that the variables are always local to a called routine.
Character arrays are called Strings, they are terminated by a '\0' character which may not be the part of our actual string but is very much a part of the character array. Besides this they work just like an integer array.
char str[4] = "abhi";
//this will lead to error that the string is too long beacuse we need one element (last element) of a character array for '\0' character
When using external variables before even defining them in the souce file we might have to declare them using - extern keyword.
int foo()
{
extern int num;
//other statements
}
int num = 2; //external variable
main()
{
foo();
}
Note that the external variables are also there when we don’t need them, so we must avoid using them too much.