PL Week 3 Material

INCOMPLETE

“C is a middle-level programming language.”

Briefly explains what this means.

C combines features of low-level (memory, hardware access) & high-level (functions, modular code) programming languages.

“C is structured and modular.”

Briefly explains what this means.

C uses functions to divide programs into manageable blocks of code, which makes debugging reuse easier.

“C has efficient I/O (input/output).”

Briefly explains what this means.

• scanf() for direct access to input operations

• printf() for direct access to output operations

scanf() uses ____________ input, which can affect…

scanf() uses buffered input, which can affect how strings and newlines are handled.

You should always check return values from scanf() to ensure….

You should always check return values from scanf() to ensure…. input was correctly received.

Mismatching format specifiers (e.g., %d for a float) may cause ____________ behaviour.

Mismatching format specifiers (e.g., %d for a float) may cause undefined behaviour.

T or F: C is a case-sensitive language.

True

T or F: C treats Variable and variable as different identifiers.

True because C is case-sensitive

Every _________ in C must end with a semi-colon.

Every statement in C must end with a semi-colon.

Name 2 things curly braces are used for in C.

1. Used to define blocks of code, especially for if, loops, and functions.

//Example
if (x > 0) {
    printf("Positive\n");
    x = x - 1;
}

(2) Helps group multiple statements.

//Example
#include <stdio.h>

int main() {
    int x = 10;

    if (x > 5) {
        printf("x is greater than 5\n");
        x = x - 1;
        printf("x is now %d\n", x);
    }

    return 0;
}

//Without { }, only one statement would be part of the if.

//With { }, it groups multiple statements as one block under the if.

T or F: In C, a main() function is NOT mandatory.

False.

What are the two forms of main() function accepted in C?

//Opt 1
int main() 

//Opt 2 
void main()  // non-standard, but accepted in many compilers

(a) Name the 3 categories of data types.

(b) Then name the main types within each category, their size, and their range.

(1) BASIC (PRIMARY)

Type	Size	Range
int	2 bytes	-32,768 to 32,767
char	1 byte	-128 to 127
float	4 bytes	~±3.4 × 10⁻³⁸ to 10³⁸
double	8 bytes	~±1.7 × 10⁻³⁰⁸ to 10³⁰⁸

(2) MODIFIED

Type	Size	Description
unsigned int	2	0 to 65,535
long int	4	Larger range than int
short int	2	Smaller range
unsigned char	1	0 to 255

(3) DERIVED

• Arrays

• Pointers

• Structures

• Unions

(a) What is a pointer?

(b) Syntax?

(a) A pointer is a variable that stores the memory address of another variable.

(b) Syntax:

//Syntax

int x = 10;

int *p = &x; // 'p' holds the address of x

Operator
&

What’s its meaning?

Operator	Meaning
&	"Address of" operator

Operator
*

What’s its meaning?

INCOMPLETE

In order to use a pointer, you must always..

Initialize the pointer before using it.

Uninitialized pointers can cause…

INCOMPLETE

Which types of statements in C govern the flow of execution?

🔹 if, if-else, and nested if-else

Describe what each is used for in 1 sentence:

(a) if, if-else, and nested if-else

(b) switch Statement

(a) if, if-else, and nested if-else

Used to selectively execute code based on one or more Boolean conditions, with nested if-else handling multiple layered decisions.

Example:

if (x > y) {
  printf("x is greater");
} else {
  printf("y is greater");
}

(b) switch Statement

Used for multi-way branching, efficiently executing code based on the value of a single expression (usually an integer or enum).

Example:

  printf("y is greater");
}

(c) while Loop

• Unknown number of iterations

• Executes a block of code repeatedly as long as the condition is true, checking the condition before the first iteration.

(d) do-while Loop

• Executes a block of code at least once, and then continues looping while the condition remains true (condition is checked after the loop body).

• A

(e) for Loop

Describe what each is used for in 1 sentence. Then specify when the loop condition is evaluated — that is, whether the loop checks the condition before (entry) or after (exit) executing the loop body.

(a) while Loop

(b) do-while Loop

(c) for Loop

Loop Type	Entry/Exit	Used For
while	Entry	Unknown iterations (check before)
do-while	Exit	At least one iteration guaranteed
for	Entry	Count-controlled iterations

Briefly what “Jump” statements do:

(a) break

(b) continue

🔹 Jump Statements

• break: Exit loop or switch

• continue: Skip to next iteration

&&

(a) Type of operator?

(b) Function

(a) Type: Logical operator

(b) Function:

• Used to combine two Boolean conditions.

• The result is true (1) only if both conditions are true; otherwise, it evaluates to false (0).

if (x > 0 && x < 10)
{
    printf("x is between 1 and 9\n");
}