CS 161
Introduction to Programming
and Problem Solving
Chapter 12
C++ Statements
Herbert G. Mayer, PSU
Status 10/8/2014
Initial content copied verbatim from
ECE 103 material by prof. Phillip Wong @ PSU
Syllabus




Individual Statements
Statement Bocks
Examples
List of C Operators
Individual C++ Statements
 A statement is a valid combination of keywords and
expressions that forms a complete action
 Expressions consists of operands and combining
operators; list of operators below
 Statements are executed in sequence to accomplish
a specified task
 Individual statements are terminated by semicolon ;
 An additional semicolon by itself creates a null
statement; null statements generate no code
2

A statement block (AKA a compound statement) is a
sequence of 0 or more statements grouped together
{ // opening brace, marks the start of the block
} // ending brace, marks the end of the block
Syntax:
{
statement;
statement;
:
}
There is no need for a semicolon after the ending brace.
3

Variables declared outside a block can be accessed
from inside the block, unless overridden; they are
said to be global to the inner scope

Variables can be declared inside a block:
 These variables have local scope
 Inside the block, a local variable takes precedence
over a variable having the same name from outside
the block; i.e. a search for names progresses from
inner toward outer scopes
4
#include <stdio.h>
#include <stdio.h>
/* All variables in same scope */
int main( void )
{ // main
int x, y;
/* Scope depends on block */
int main (void)
{ // main
int x, y;
x = 2;
y = 3 * x;
printf( "A: %d %d\n", x, y );
x = 2;
y = 3 * x;
printf( "A: %d %d\n", x, y );
x = 4;
y = 3 * x;
printf( "B: %d %d\n", x, y );
{ // a new block
int x;
x = 4;
y = 3 * x;
printf( "B: %d %d\n", x, y
printf( "C: %d %d\n", x, y );
return 0;
} //end main
);
} //end of block
printf( "C: %d %d\n", x, y );
return 0;
} //end main
Output:
Output:
A: 2 6
B: 4 12
C: 4 12
A: 2 6
B: 4 12
C: 2 12
5
#include <stdio.h>
/* Scope depends on block */
int main( void )
{ // main
int x = 1, y = 10;
printf( "A: %d %d\n", x, y );
{ // new block, level 2
int x = 3;
printf("B: %d %d\n", x, y);
x = 5; y = 20;
printf("C: %d %d\n", x, y);
{ // new nested block, level 3
int x = 7;
printf( "D: %d %d\n", x, y
);
y = 30;
printf( "E: %d %d\n", x, y
A variable's scope
determines its
visibility or
accessibility from
other parts of a
program.
);
} //end boxck level 3
printf( "F: %d %d\n", x, y );
} //end block level 2
printf( "G: %d %d\n", x, y );
return 0;
} //end main
6
#include <stdio.h>
/* Scope depends on block */
int main( void )
{ // main
int x = 1, y = 10;
printf( "A: %d %d\n", x, y );
A: 1 10
{ // new block, level 2
int x = 3;
B: 3 10
printf("B: %d %d\n", x, y);
x = 5; y = 20;
printf("C: %d %d\n", x, y);
C: 5 20
{ // new nested block, level 3
int x = 7;
printf( "D: %d %d\n", x, y
D: 7 20
);
y = 30;
printf( "E: %d %d\n", x, y
E: 7 30
);
} //end block level 3
printf( "F: %d %d\n", x, y );
} //end block level 2
F: 5 30
G: 1 30
printf( "G: %d %d\n", x, y );
return 0;
} //end main
7
Table 1: C Operator Precedence Table in Decreasing Order
L
1
2
Description
Function call
( )
Array subscript
[ ]
Struct member
.
Struct dereference
expr++
Decrement (post)
expr--
Associativity
L
5
left-to-right
6
Description
Operator
Bitwise left shift
<<
Bitwise right shift
>>
Less than
<
Greater than
>
LT or equal to
<=
GT or equal to
>=
Equal to
==
Not equal to
!=
Associativity
left-to-right
left-to-right
Indirection
*
Reference (addr)
&
Unary plus
+
8
Bitwise AND
&
left-to-right
Unary minus
-
9
Bitwise XOR
^
left-to-right
Logical negation
!
10
Bitwise OR
|
left-to-right
11
Logical AND
&&
left-to-right
Bitwise NOT
~
7
right-to-left
left-to-right
Increment (pre)
++expr
12
Logical OR
||
left-to-right
Decrement (pre)
--expr
13
Conditional
? :
right-to-left
14
Assignment
= += -= *= /=
%= >>= <<=
&= ^= |=
right-to-left
15
Comma
,
left-to-right
Size in bytes
4
->
Increment (post)
Cast
3
Operator
( type )
sizeof
Multiplication
*
Division
/
Modulo
%
Addition
+
Subtraction
-
left-to-right
Highest precedence is Level 1.
Lowest precedence is Level 15.
left-to-right
8