This document discusses call by reference and call by value as two methods for passing arguments to functions. Call by value passes the value of an argument, so changes to the parameter inside the function do not affect the original argument. Call by reference passes the address of an argument, allowing the function to manipulate the original argument. The document provides examples of call by reference, showing how it allows functions to return multiple values by changing original arguments. It poses questions about example code outputs to illustrate the differences between call by value and call by reference.

1. Lecture 14Lecture 14
Version 1.0Version 1.0
Call by ReferenceCall by Reference

2. 2Rushdi Shams, Dept of CSE, KUET, Bangladesh
Methods to pass argumentsMethods to pass arguments
 Arguments can generally be passed to functionsArguments can generally be passed to functions
in one of the two ways:in one of the two ways:
(a) sending the values of the arguments(a) sending the values of the arguments
(b) sending the addresses of the arguments(b) sending the addresses of the arguments

3. 3Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by valueCall by value
 ‘‘value’ of each of the actual arguments in thevalue’ of each of the actual arguments in the
calling function is copied into correspondingcalling function is copied into corresponding
formal arguments of the called functionformal arguments of the called function
 changes made to the formal arguments in thechanges made to the formal arguments in the
called function have no effect on the values ofcalled function have no effect on the values of
actual arguments in the calling functionactual arguments in the calling function

4. 4Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by valueCall by value

5. 5Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by ReferenceCall by Reference
 the addresses of actual arguments in the callingthe addresses of actual arguments in the calling
function are copied into formal arguments offunction are copied into formal arguments of
the called functionthe called function
 using these addresses we would have an accessusing these addresses we would have an access
to the actual arguments and hence we would beto the actual arguments and hence we would be
able to manipulate themable to manipulate them

6. 6Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by ReferenceCall by Reference
a
10
65000
b
20
60000
x
65000
70000
y
60000
75000
t
10
80000
20 10

7. 7Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by referenceCall by reference
 Using a call by reference intelligently we canUsing a call by reference intelligently we can
make a function return more than one value at amake a function return more than one value at a
time, which is not possible ordinarilytime, which is not possible ordinarily

8. 8Rushdi Shams, Dept of CSE, KUET, Bangladesh
Call by referenceCall by reference

9. 9Rushdi Shams, Dept of CSE, KUET, Bangladesh
What is the output?What is the output?

10. 10Rushdi Shams, Dept of CSE, KUET, Bangladesh
What will be the output?What will be the output?

11. 11Rushdi Shams, Dept of CSE, KUET, Bangladesh
What will be the output?What will be the output?

12. 12Rushdi Shams, Dept of CSE, KUET, Bangladesh
What will be the output?What will be the output?