1. Engr 0012 (04-1) LecNotes 21-01

2. functions & parameter/argument lists
formal parameters
are found in prototype
and definition
ca20a.cpp
// prototypes
void fcn1( int b, int a );
main()
{ // begin main
// variable declaration
int a = 5, b = 7;
// algorithm
printf( "\nIN main - Before call to fcn1"
"\n a = %d, b = %d ", a, b );
fcn1( a, b );
printf( "\nIN main - After call to fcn1"
"\n\n a = %d, b = %d ", a, b );
} // end main
//**************************************
void fcn1( int b, int a )
{ // begin fcn1
b = b*a;
a = a+b;
printf( "\n\nIn fcn1:"
" a = %d, b = %d ", a, b );
} // end fcn1
listed singly with data type
actual parameters
actual parameters are
found in calling statment
listed singly w/o data type
both formal & actual parameters
are value parameters
values transferred from
calling statement to function for use
original values cannot be altered by function
Engr 0012 (04-1) LecNotes 21-02

3. functions & parameter/argument lists
memory map/trace
ca20a.cpp
// prototypes
void fcn1( int b, int a );
main()
{ // begin main
// variable declaration
int a = 5, b = 7;
// algorithm
printf( "\nIN main - Before call to fcn1"
"\n a = %d, b = %d ", a, b );
fcn1( a, b );
printf( "\nIN main - After call to fcn1"
} // end main
//**************************************
void fcn1( int b, int a )
{ // begin fcn1
b = b*a;
a = a+b;
printf( "\n\nIn fcn1:"
" a = %d, b = %d ", a, b );
} // end fcn1
IN main - before call to fcn1
a = 5, b = 7
In fcn1: a = 42, b = 35
IN main - after call to fcn1
Engr 0012 (04-1) LecNotes 21-03

4. functions & parameter/argument lists
formal parameters
are found in prototype
and definition
ca20b.cpp
// prototypes
void fcn2( int *pb, int *pa );
main()
{ // begin main
// variable declaration
int a = 5, b = 7;
// algorithm
printf( "\nIn main - before call to fcn2"
"\n a = %d, b = %d ", a, b );
fcn2( &a, &b );
printf( "\n\nIn main - after call to fcn2"
} // end main
//**************************************
void fcn2( int *pb, int *pa )
{ // begin fcn2
(*pb) = (*pb)*(*pa);
(*pa) = (*pa)+(*pb);
printf( "\n\nIn fcn2,"
" a = %d, b = %d ", *pa, *pb );
} // end fcn2
listed singly with data type
actual parameters
actual parameters are
found in calling statment
listed singly w/o data type
formal & actual parameters
are address or pointer
parameters
addresses transferred from calling statement to function for use
original values can be altered by function
Engr 0012 (04-1) LecNotes 21-04

5. functions & parameter/argument lists
ca20b.cpp
// prototypes
void fcn2( int *pb, int *pa );
main()
{ // begin main
// variable declaration
int a = 5, b = 7;
// algorithm
printf( "\nBefore call,"
" a = %d, b = %d ", a, b );
fcn2( &a, &b );
printf( "\n\nAfter call,"
} // end main
//**************************************
void fcn2( int *pb, int *pa )
{ // begin fcn2
(*pb) = (*pb)*(*pa);
(*pa) = (*pa)+(*pb);
printf( "\n\nIn fcn2,"
" a = %d, b = %d ", *pa, *pb );
} // end fcn2
memory map/trace
In main - before call to fcn2
a = 5, b = 7
In fcn2: a = 42, b = 35
In main – after call to fcn2
a = 35, b = 42
Engr 0012 (04-1) LecNotes 21-05

6. functions & parameter/argument lists
LecNotes21a.cpp
void fcn3( int x, int y, int *pq, int *pr );
//************************************************
main()
{ // begin main
// variable declaration
int a = 5, b = 7, c, d;
// algorithm
printf( "\nBefore call: "
" a = %d, b = %d, c = %d, d = %d",
a, b, c, d );
fcn3( a, b, &c, &d );
printf( "\n\nAfter call: :
"\n a = %d, b = %d, c = %d, d = %d",
} // end main
void fcn3( int b, int a, int *pq, int *pr )
{ // begin fcn3
int h = 2;
*pq = h*(a + b);
*pr = a*b/h;
printf( "\n\nIn fcn3: "
" a = %d, b = %d, *pq = %d, *pr = %d ",
a, b, *pq, *pr );
} // end fcn3
formal & actual parameters
are both value and address
or pointer parameters
formal parameters
actual parameters
both values and addresses transferred from calling statement to function for use
only values referred to by address parameters can be altered by function
Engr 0012 (04-1) LecNotes 21-06

7. functions & parameter/argument lists
memory map/trace
LecNotes21a.cpp
void fcn3( int x, int y, int *pq, int *pr );
//************************************************
main()
{ // begin main
// variable declaration
int a = 5, b = 7, c, d;
// algorithm
printf( "\nBefore call: "
" a = %d, b = %d, c = %d, d = %d",
a, b, c, d );
fcn3( a, b, &c, &d );
printf( "\n\nAfter call: :
"\n a = %d, b = %d, c = %d, d = %d",
} // end main
void fcn3( int b, int a, int *pq, int *pr )
{ // begin fcn3
int h = 2;
*pq = h*(a + b);
*pr = a*b/h;
printf( "\n\nIn fcn3: "
" a = %d, b = %d, *pq = %d, *pr = %d ",
a, b, *pq, *pr );
} // end fcn3
Before call: a = 5, b = 7, c = ??, d = ??
In fcn3: a = 7, b = 5, *pq = 24, *pr = 17
After call: a = 5, b = 7, c = 24, d = 17
Engr 0012 (04-1) LecNotes 21-07