CS 107: Pictures and Sounds: Programming with Multimedia

Spring 2008

For what possible values of x are statements A and B executed in the following two pieces of code?

First piece of code:

if (x >= 3):
    if (x == 7):
       statement A 

    else:
	statement B

Second piece of code:

if (x >= 3):
    if (x == 7):
       statement A 
else:
   statement B

Explain the difference between the following two pieces of code. For each piece of code assume that the variables x and y have been defined and assigned a value before reaching this section.
1. First piece of code:
```
s = 0
if ( x > 0 ):
    s = s + 1
if ( y > 0 ):
    s = s + 1
```
2. Second piece of code:
```
s = 0
if ( x > 0 ):
    s = s + 1
elif ( y > 0 ):
    s = s + 1
```
What does the following for statement do? Assume that n is some positive integer.
```
for b in range(n, 0, -1):
    print b
```
For the following loops, indicate what gets printed. (Note that str is a function that takes a number and returns the corresponding string. For example str(3) returns the string "3".)
1. First piece of code:
```
for x in range(4):
   for y in range(1, 4):
       print str(x) + ", " + str(y)
```
2. Second piece of code:
```
for x in range(4):
   for y in range(x, 4):
       print str(x) + ", " + str(y)
```