what does printf returns

"printf returns the number of charecters printed" 

#include<stdio.h>
#include<conio.h>


int main()
{
    int k=0;
    k=printf("kdhsafuh");
    printf("\nk=%d",k);
    getch();
    return 0;
}

output:k=8

Merge with c

c programm to count the number of lines

#include <stdio.h>

/* count lines in input */

main()

{

int c, nl;

nl = 0;

while ((c = getchar()) != EOF)

if (c == '\n')

++nl;

printf("%d\n", nl);

}

The following program erases the file specified on the command line.

#include <stdio.h>

#include <stdlib.h>

#include <ctype.h>

int main(int argc, char *argv[])

{

char str[80];

if(argc!=2) {

printf(''usage: xerase <filename>\n");

exit(1);

}

printf("Erase %s? (Y/N): ", argv[1]);

gets(str);

if(toupper(*str)=='Y')

if(remove(argv[1])) {

printf("Cannot erase file.\n");

exit(1);

}

return 0;

}

declaration vs definition

A declaration provides basic attributes of a symbol: its type and its name. A definition provides all of the details of that symbol--if it's a function, what it does; if it's a class, what fields and methods it has; if it's a variable, where that variable is stored. Often, the compiler only needs to have a declaration for something in order to compile a file into an object file, expecting that the linker can find the definition from another file. If no source file ever defines a symbol, but it is declared, you will get errors at link time complaining about undefined symbols.

 

identifier in c and c++

In C, identifiers may be of any length. However, not all characters will necessarily be significant. C defines two kinds of identifiers: external and internal. An external identifier will be involved in an external link process. These identifiers, called external names, include function names and global variable names that are shared between source files. If the identifier is not used in an external link process, then it is internal. This type of identifier is called an internal name and includes the names of local variables, for example. In C89, at least the first 6 characters of an external identifier and at least the first 31 characters of an internal identifier will be significant. C99 has increased these values. In C99, an external identifier has at least 31 significant characters, and an internal identifier has at least 63 significant characters. As a point of interest, in C++, at least the first 1,024 characters of an identifier are significant. These differences may be important if you are converting a program from C89 to C99, or from C to C++.

keep in mind while compiling the c programme in an c++ compiler

In general, you can use a C++ compiler to compile a C program. In fact, today most compilers

handle both C and C++ programs. Thus, most programmers will use a C++ compiler to compile

their C code! However, since C++ was built upon the 1989 C standard, you must restrict your C

code to the features defined by that standard .(yor are not permited to use the features of c99)

There is one thing that you must be careful about when using a C++ compiler to compile a C

program: the file extension. By convention, C programs use the .C extension. C++ programs

use .CPP. Don't accidentally give your C program a .CPP extension. Differences between the two

languages might prevent a valid C program from being compiled

as if it were a C++ program. By

specifying the .C extension, you are telling the C++ compiler to perform a ''C compile.