C Programming Syllabus

What is a variable in C?

A named storage location in memory whose value can be changed during program execution, associated with a specific data type.

State three rules for naming a valid identifier (variable name) in C.

Must begin with a letter or underscore; can contain only letters, digits, and underscores; cannot be a reserved keyword; and is case-sensitive.

What is the difference between declaring and initializing a variable in C?

Declaration allocates storage and specifies the type (e.g. int x;); initialization assigns an initial value at declaration (e.g. int x = 5;).

What are the four storage classes in C?

auto, register, static, and extern.

What does the static storage class do to a local variable?

It preserves the variable's value between function calls and limits its scope to the block, giving it a lifetime equal to the whole program.

What is a constant in C, and name two ways to define one.

A constant is a fixed value that cannot be changed during execution. Define via the #define preprocessor directive or the const keyword.

What is the difference between #define PI 3.14 and const float PI = 3.14;?

#define is a preprocessor macro (text substitution, no type, no memory); const creates a typed, read-only variable stored in memory that obeys scope rules.

How do you write a character constant, a string constant, and an octal integer constant in C?

Character: 'A' (single quotes); String: "Hello" (double quotes); Octal: leading 0, e.g. 0755.

List the five arithmetic operators in C and give the result of $17 \% 5$.

Addition +, subtraction -, multiplication *, division /, and modulus %. $17 \bmod 5 = 2$.

In C, what is the result of the integer expression $7 / 2$ and why?

It is $3$, because integer division truncates the fractional part (both operands are integers).

What does the modulus operator % require of its operands, and what is $-7 \% 3$ typically in C99+?

Both operands must be integers; in C99+ the result takes the sign of the dividend, so $-7 \% 3 = -1$.

List the six relational operators in C.

$<$ (less than), $>$ (greater than), $\leq$ (<=), $\geq$ (>=), $==$ (equal to), and $\neq$ (!=).

What value does a relational expression evaluate to in C when it is true and when it is false?

True evaluates to $1$ and false evaluates to $0$ (of type int).

What is the common bug caused by confusing == with = in a condition?

Using = (assignment) instead of == (comparison) assigns a value and evaluates to that value, often making the condition unintentionally true; e.g. if(x = 5) is always true.

Name the three logical operators in C and what each requires.

Logical AND &&, logical OR ||, and logical NOT !. && and || are binary; ! is unary.

What is "short-circuit evaluation" for the && and || operators?

For &&, if the left operand is false (0), the right is not evaluated; for ||, if the left is true (nonzero), the right is not evaluated.

Given $a=5, b=0$, what is the value of the expression $a \;\&\&\; b$ and $a \;||\; b$ in C?

$a \;\&\&\; b = 0$ (false, since b is 0); $a \;||\; b = 1$ (true, since a is nonzero).

List the six bitwise operators in C.

AND &, OR |, XOR ^, NOT (complement) ~, left shift <<, and right shift >>.

What is the result of $5 \;\&\; 3$ and $5 \;|\; 3$ in C (bitwise)?

$5 \;\&\; 3 = 1$ (0101 AND 0011 = 0001); $5 \;|\; 3 = 7$ (0101 OR 0011 = 0111).

What arithmetic effect does a left shift by n bits ($x$ << $n$) have on an unsigned integer?

It multiplies the value by $2^{n}$ (equivalent to $x \times 2^{n}$), filling vacated bits with 0.

What does the bitwise XOR (^) operator return for each bit, and what is $6 \;\hat{}\; 3$?

XOR returns 1 when the two bits differ, 0 when they are the same; $6 \;\hat{}\; 3 = 5$ (0110 XOR 0011 = 0101).

What is the simple assignment operator, and give three examples of compound assignment operators.

Simple assignment is =. Compound examples: +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=.

What is x += 5 shorthand for, and what does it require of x?

It is shorthand for x = x + 5; x must be a modifiable lvalue (an assignable variable).

Name five of the miscellaneous operators in C (beyond arithmetic/relational/logical).

sizeof, the address-of operator &, the dereference operator *, the ternary conditional operator ?:, the comma operator, and the member operators . and ->.

What does the ternary/conditional operator syntax look like, and rewrite "if a>b then max=a else max=b" using it?

Syntax: condition ? expr_if_true : expr_if_false. Rewritten: max = (a > b) ? a : b;

What does the sizeof operator return, and what is the type of its result?

It returns the size in bytes of a type or variable; the result is of type size_t (an unsigned integer type).

What is the difference between the prefix (++x) and postfix (x++) increment operators?

Prefix ++x increments then yields the new value; postfix x++ yields the original value then increments.

Name the three main conditional (selection) statement forms in C.

The if statement, the if-else (and else-if ladder) statement, and the switch statement.

What are the key restrictions on the switch statement's controlling expression and its case labels?

The expression must evaluate to an integer or character (integral) type, and each case label must be a unique constant integral expression.

What is the purpose of break in a switch statement, and what happens without it?

break exits the switch after a matching case; without it, execution "falls through" and continues into subsequent cases.

Name the three loop constructs in C and state which one guarantees at least one execution of its body.

for, while, and do-while loops; the do-while loop always executes its body at least once because the condition is tested after the body.

What are the three components of a for loop header, in order?

Initialization, condition (test), and update/increment expression, written as for(init; condition; update).

What is the key structural difference between a while loop and a do-while loop?

A while loop tests the condition before the body (entry-controlled); a do-while tests after the body (exit-controlled), so do-while runs at least once.

List the four jump statements in C.

break, continue, goto, and return.

What is the difference between break and continue inside a loop?

break terminates the entire loop immediately; continue skips the rest of the current iteration and proceeds to the next iteration.

What does the return statement do in a function, and what must it return in a function declared void?

return exits the function and optionally passes a value back to the caller; in a void function it returns nothing (just "return;").

What is a function in C, and what are its three related parts a programmer defines/uses?

A function is a self-contained block of reusable code that performs a task. The three parts are the function declaration (prototype), the function definition, and the function call.

What is a function prototype, and why is it used?

A declaration specifying the function's return type, name, and parameter types (e.g. int add(int, int);); it tells the compiler how to call the function before its definition appears.

In the function definition int sum(int a, int b), what is the return type and what are a and b called?

The return type is int; a and b are the formal parameters (or formal arguments).

What are the two primary methods of parameter passing in C, and which one does C use by default?

Call by value and call by reference (via pointers); C passes arguments by value by default.

In call by value, what happens to the original argument when the function modifies its parameter?

Nothing—the function works on a copy, so changes to the parameter do not affect the original variable in the caller.

How is "call by reference" achieved in C, and why does it allow a function to modify the caller's variable?

By passing the address of a variable (a pointer) and dereferencing it inside the function; the function accesses the original memory location directly, so changes persist.

When you pass an array to a function in C, what is actually passed, and what is the effect?

A pointer to the array's first element is passed (the array decays to a pointer), so the function can modify the original array elements (effectively call by reference).