1. ECE 103 Engineering Programming Chapter 12 More C Statements
Herbert G. Mayer, PSU CS
Status 7/11/2015
Initial content copied verbatim from
ECE 103 material developed by
Professor Phillip PSU ECE

2. Syllabus
Individual Statements
Statement Blocks

3. Individual Statements
A statement is a valid combination of keywords and expressions that forms a complete action
A C program consists of statements that are executed in sequence to accomplish a specified task
Individual statements are terminated by a semicolon ;
Syntax:
statement;
An additional semicolon by itself creates a NULL statement; null statements generate no code 2

4. Statement Blocks
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; }
There is no need for a semicolon after the ending brace. 3

5. Variables can be declared inside a block:
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

6. 5 #include <stdio.h> /* All variables in same scope */
int main( void )
{ // main
int x, y;
x = 2;
y = 3 * x;
printf( "A: %d %d\n", x, y );
x = 4;
printf( "B: %d %d\n", x, y );
printf( "C: %d %d\n", x, y );
return 0;
} //end main
Output:
A: 2 6
B: 4 12
C: 4 12
#include <stdio.h>
/* Scope depends on block */
int main (void)
{ // main
int x, y;
x = 2;
y = 3 * x;
printf( "A: %d %d\n", x, y );
{ // a new block
int x;
x = 4;
printf( "B: %d %d\n", x, y );
} //end of block
printf( "C: %d %d\n", x, y );
return 0;
} //end main
Output:
A: 2 6
B: 4 12
C: 2 12 5

7. #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 );
} //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
A variable's scope determines its visibility or accessibility from other parts of a program. 6

8. 7 #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 );
} //end block level 3
printf( "F: %d %d\n", x, y );
} //end block level 2
printf( "G: %d %d\n", x, y );
return 0;
} //end main 7

9. 8 #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 );
} //end block level 3
printf( "F: %d %d\n", x, y );
} //end block level 2
printf( "G: %d %d\n", x, y );
return 0;
} //end main
A: 1 10
B: 3 10
C: 5 20
D: 7 20
E: 7 30
F: 5 30
G: 1 30 8