functions in C

functions in C

• 1.
  M E HW I S H M E H M O O D
• 2.
  • A functionis a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions. • You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division usually is so each function performs a specific task.
• 3.
  A function inC can have a value, a side effect, or both • The side effect occurs before the value is returned. • The function’s value is the value of the expression in the return statement. • A function can be called for its value, its side effect, or both.
• 5.
  • The generalsyntax of a function in C is : • The type_specifier specifies the data type of the value, which the function will return. • A valid function name is to be assigned to identify the function • Arguments appearing in parentheses are also termed as formal parameters.
• 6.
  //Prototype declaration void greeting(); intmain() { greeting(); return 0; } // main Void greeting() { printf(“HELLO WORLD”); return ; } //greeting() Declaration is coded first Definition is after the call Call is in the statement sections
• 8.
  The type ofthe expression in the return statement must match the return type in the function header. . Only one value can be returned by a function
• 9.
  • Formal parametersare variables that are declared in the header of the function definition. • Actual parameters are the expressions in the calling statement. • The formal and actual parameters must match exactly in type, order, and number. Their names, however, do not need to be the same.
• 10.
  int square(int x); Intmain() { Int I For(i=1;i<10; i++) { printf(“n square of %d is %d:”, i, square(i)); } int square(int x) { int j; j=x*x; return(j); } Actual argument Formal argument
• 11.
  • Scope Rules- Rules that govern whether one piece of code knows about or has access to another piece of code or data • The code within a function is private or local to that function • Two functions have different scopes • One function cannot be defined within another function
• 12.
   Call byvalue  Call by reference
• 13.
   When argumentsare passed to the called function, the values are passed through temporary variables
• 14.
  • In callby reference, the function is allowed access to the actual memory location of the argument and therefore can change the value of the arguments of the calling routine
• 16.
  main() { . . palindrome(); . . } palindrome() { . . getstr(); reverse(); cmp(); . . }
• 18.
  • A pointervariable can be passed as a parameter to a function either by value or by reference. • In the function pointer Parameters, both p and q are pointers. The parameter p is a reference parameter; the parameter q is a value parameter. • Furthermore, the function pointer Parameters can change the value of *q, but not the value of q. However, the function pointer Parameters can change the value of both p and *p.