Weekly Quizzes — W01 to W04

10 questions each · ~15 min each · attempt ALL ten before opening the key · Hub · W05–W08 →

W01 — Programs, compiling, first output (Week 1)

Q1. [Easy] The edit–compile–run cycle is best described as…

a) edit, then run, then compile if it fails
b) edit the source, compile it into an executable, run the executable
c) compile, edit, run in any order you like
d) run the source file directly; compiling is optional

Q2. [Easy] Which file does the compiler read?

a) the executable
b) the .cpp source file
c) the terminal
d) the output of the program

Q3. [Easy] In g++ -std=c++17 -Wall -Wextra hello.cpp -o hello, the -o hello part means…

a) optimize the program
b) name the output executable hello
c) run the program once
d) open the file for editing

Q4. [Medium] Every C++ program begins executing at…

a) the first line of the file, whatever it is
b) the first function defined
c) the main function
d) #include <iostream>

Q5. [Medium] What does this print?

#include <iostream>
using namespace std;
int main() {
    cout << "3 + 4";
    return 0;
}

a) 7
b) 3 + 4
c) nothing — the expression must be outside quotes
d) an error

Q6. [Medium] A syntax error is…

a) the program running but producing wrong output
b) the compiler refusing the text because it breaks the language’s grammar
c) a crash while the program runs
d) a warning you can ignore forever

Q7. [Medium] cout << "Hi\n" versus cout << "Hi" — the difference is…

a) none; both move to a new line
b) the first prints a newline after Hi
c) the second prints a newline before Hi
d) the first is invalid

Q8. [Medium] The compiler’s warning -Wall exists because…

a) all programs must have warnings to compile
b) some legal code is suspicious, and warnings point at it before it bites
c) it makes the program run faster
d) it deletes errors automatically

Q9. [Hard] Which is a logic error?

int a = 5, b = 2;
cout << a + b * 2;   // wanted: (a + b) * 2 = 14

a) it prints 9 — legal code, wrong result
b) it prints 14
c) it fails to compile
d) it crashes

Q10. [Hard] You change your source file, but running ./hello shows the old behavior. The most likely cause is…

a) the terminal is broken
b) you never recompiled — the executable is from the old source
c) C++ programs cannot be changed
d) cout is caching the output

W01 — Answer key (open only after attempting)

Q1 — b. The cycle is edit → compile → run. The executable, not the source, is what runs.

Q2 — b. The compiler reads source text; everything else in the cycle is produced by it.

Q3 — b. -o names the output file. Without it, most compilers default to a.out (or a.exe).

Q4 — c. main is the entry point — the only function the operating system calls by name when the program starts.

Q5 — b. "3 + 4" is a string literal: characters, not an expression. Remove the quotes and cout << 3 + 4 evaluates and prints 7.

Q6 — b. Syntax errors are grammar violations caught at compile time. Wrong output (a) is a logic error; crashes (c) are runtime errors.

Q7 — b. \n is the escape character for a newline; without it, the next output continues on the same line.

Q8 — b. Warnings flag legal but suspicious code — the compiler accepts it while telling you it smells wrong. Turn warnings on; they are free bug detection.

Q9 — a. It compiles and runs, printing 9 (5 + 2·2). The intended 14 requires parentheses. Legal code, wrong answer — the definition of a logic error.

Q10 — b. The executable is a snapshot of the source at compile time. Edit-compile-run means recompiling after every edit.

W02 — Variables, types, arithmetic (Week 2)

Q1. [Easy] Which declares a whole-number variable?

a) double total;
b) int count;
c) char count;
d) bool total;

Q2. [Easy] What is stored in x after int x = 7 / 2;?

a) 3.5
b) 3
c) 4
d) an error

Q3. [Easy] 10 % 3 evaluates to…

a) 3
b) 3.33
c) 1
d) 0

Q4. [Medium] Which literal is a char?

a) "A"
b) 'A'
c) A
d) 65.0

Q5. [Medium] const int SPEED = 80; SPEED = 90; — what happens?

a) SPEED becomes 90
b) compile error: assignment to a constant
c) SPEED becomes 170
d) undefined behavior

Q6. [Medium] Which expression computes the average of int a, b correctly?

a) (a + b) / 2
b) (a + b) / 2.0
c) a / 2 + b / 2
d) double(a + b / 2)

Q7. [Medium] After int x = 5; x += 3; x *= 2; what is x?

a) 13
b) 16
c) 10
d) 11

Q8. [Medium] What does this print?

int a = 4, b = 10;
cout << a + b * 2;

a) 28
b) 24
c) 18
d) 12

Q9. [Hard] What does this print?

int p = 17;
cout << p / 5 << " " << p % 5;

a) 3.4 2
b) 3 2
c) 3 3
d) 2 3

Q10. [Hard] A program stores money as double balance = 0.1 + 0.2; and then tests balance == 0.3. The test…

a) passes — addition is exact
b) fails — 0.1 and 0.2 are not exactly representable in binary floating point
c) fails only on some compilers, so it is fine to ignore
d) crashes

W02 — Answer key

Q1 — b. int is the whole-number type. double holds decimals, char holds one character, bool holds true/false.

Q2 — b. Integer division truncates: 7/2 is 3, remainder discarded. Use 7 / 2.0 when you want 3.5.

Q3 — c. % is the remainder: 10 = 3·3 + 1. Both operands must be integers.

Q4 — b. Single quotes make a character literal; double quotes make a string ("A" is two characters plus a terminator).

Q5 — b. const means initialize-once. Assigning later is a compile error — the compiler is the guard you asked for.

Q6 — b. Dividing by 2.0 promotes the whole expression to floating point. (a) truncates; (c) truncates twice; (d) converts after the integer division inside already lost the fraction.

Q7 — b. 5 + 3 = 8; 8 × 2 = 16. Compound assignments read as “update x using the operation.”

Q8 — b. Precedence: * before + → 10 + 4 = 24. Parentheses change it to 28 — the trap the question is built on.

Q9 — b. / gives the quotient 3, % the remainder 2. Together they partition 17 = 3·5 + 2 exactly.

Q10 — b. Binary floating point cannot represent 0.1 or 0.2 exactly, so the sum is a hair off 0.3. Compare with a tolerance (fabs(balance - 0.3) < 1e-9) or store money as integer cents.

W03 — Input, output, and the buffer (Week 3)

Q1. [Easy] Which statement reads one whole number from the keyboard into age?

a) cout >> age;
b) cin >> age;
c) cin << age;
d) read(age);

Q2. [Easy] cin >> word; where the user types Ali Raza puts what in word?

a) Ali Raza
b) Ali — >> stops at the first space
c) Raza
d) nothing

Q3. [Easy] getline(cin, line); reads…

a) one word
b) one character
c) one entire line, spaces included, up to Enter
d) nothing until a number arrives

Q4. [Medium] After int n; cin >> n; the buffer still contains the Enter key. What does an immediate getline(cin, s) usually get?

a) the user’s next line
b) an empty string — it consumes the leftover newline
c) a compile error
d) the number n again

Q5. [Medium] Which prints Total: 12.50?

a) cout << "Total: " << 12.5;
b) cout << fixed << setprecision(2) << "Total: " << 12.5;
c) cout << "Total: %.2f" << 12.5;
d) print("Total: 12.50")

Q6. [Medium] What does this print for input 7 8?

int a, b;
cin >> a >> b;
cout << a + b;

a) 78
b) 15
c) 7 8
d) an error

Q7. [Medium] The standard fix after cin >> n; and before getline is…

a) cin.clear();
b) cin.ignore();
c) cin.getline();
d) nothing — it works automatically

Q8. [Medium] What does this print?

cout << setw(6) << 42 << "|";

(with <iomanip> included)

a) 42|
b) ` 42 ` — right-aligned in width 6
c) 42 |
d) ######42|

Q9. [Hard] What does this print for input 5?

int x;
cin >> x;
cout << "got " << x << endl << "done";

a) got 5done
b) got 5 then done on the next line
c) got 5 done
d) nothing

Q10. [Hard] A program reads a mark with cin >> mark; and the user types abc. What is true of mark afterwards?

a) it is 0 and the stream is still fine
b) the read fails: mark is unchanged (or 0 since C++11) and the stream is in a fail state until cleared
c) the program crashes
d) it holds the string “abc”

W03 — Answer key

Q1 — b. cin with >> extracts; the arrows point from the stream into the variable.

Q2 — b. >> is whitespace-delimited: it stops at the first space and leaves Raza for the next read. Whole lines need getline.

Q3 — c. getline reads to the end of the line and consumes the newline; spaces are kept.

Q4 — b. The leftover newline satisfies getline immediately — the classic mixing trap. Fix with one cin.ignore() between the >> and the getline.

Q5 — b. fixed + setprecision(2) formats decimals; the header is <iomanip>. (a) prints 12.5; (c) is C’s printf syntax, not C++ streams.

Q6 — b. Two >> reads across the same line work naturally: 7 then 8, sum 15.

Q7 — b. cin.ignore() discards the buffered newline. cin.clear() resets a failed stream — a different problem.

Q8 — b. setw(6) pads to 6 columns, right-aligned by default: four spaces then 42. setw applies to the next output only.

Q9 — b. endl outputs a newline (and flushes); the second << chain continues on the new line.

Q10 — b. >> into an int expects digits; abc fails the read, the stream enters a fail state (further reads do nothing until clear()), and the variable is zeroed (C++11) — never trusted input. This is why validation exists.

W04 — Selection: if, else-if, switch (Week 4)

Q1. [Easy] Which condition is true when mark is exactly 50 and passing means 50 or above?

a) mark > 50
b) mark >= 50
c) mark = 50
d) mark => 50

Q2. [Easy] What does this print for x = 5?

if (x > 3) cout << "A";
else       cout << "B";

a) A
b) B
c) AB
d) nothing

Q3. [Easy] In a switch, what does break do?

a) ends the program
b) exits the switch — without it, execution falls into the next case
c) skips the default case
d) restarts the switch

Q4. [Medium] What does this print for age = 15?

if (age < 13)      cout << "CHILD";
else if (age < 20) cout << "TEEN";
else               cout << "ADULT";

a) CHILD
b) TEEN
c) ADULT
d) CHILDTEEN

Q5. [Medium] bool ok = (a > 0) && (b > 0); with a = 4, b = -1 gives…

a) true
b) false
c) a compile error
d) 4

Q6. [Medium] What does this print for n = 3?

switch (n) {
    case 1: cout << "one "; break;
    case 3: cout << "three ";
    case 5: cout << "five "; break;
    default: cout << "other";
}

a) three
b) three five — case 3 has no break, so it falls through
c) three five other
d) nothing

Q7. [Medium] Which tests “n is between 1 and 100 inclusive”?

a) 1 <= n <= 100
b) n >= 1 && n <= 100
c) n >= 1 || n <= 100
d) n > 0 && n < 100

Q8. [Medium] What does this print for temp = 40?

if (temp > 35)
    cout << "HOT";
    cout << " day";

a) HOT day
b) day
c) HOT
d) nothing

Q9. [Hard] What does this print for x = 7?

int y = (x % 2 == 0) ? x / 2 : x * 3 + 1;
cout << y;

a) 3
b) 22
c) 14
d) 7

Q10. [Hard] The ladder if (m < 50) FAIL; else if (m < 70) PASS; else if (m < 70) RETRY; — why is the third branch unreachable?

a) because FAIL catches everything
b) because any mark that failed < 50 in the first test cannot re-enter; and any mark reaching the third test already satisfied < 70 in the second — the condition is always false there
c) because else-if chains need different variables
d) it is reachable for m = 70

W04 — Answer key

Q1 — b. “50 or above” is >=. Option (c) is assignment, not comparison — and (d) is not an operator at all.

Q2 — a. 5 > 3 is true, so only the if-branch runs. The else is skipped, never both.

Q3 — b. break leaves the switch. Fallthrough — running into the next case — is legal but almost always unintended; comment it if you ever mean it.

Q4 — b. 15 fails < 13, satisfies < 20 → TEEN. The ladder’s implicit ranges come from earlier tests failing.

Q5 — b. && needs both sides true. The first is true, the second false → false. Short-circuit evaluation means b > 0 may not even run.

Q6 — b. Case 3 matches, prints three , has no break, falls through to case 5 printing five , whose break exits. Fallthrough demonstrated deliberately.

Q7 — b. Each comparison stands alone and && joins them. Option (a) is the classic wrong translation — it parses as (1 <= n) <= 100, always true. Option (c)’s || is nearly everything.

Q8 — b. Without braces, only the first statement belongs to the if; cout << " day"; is unconditional. Indentation lied — braces are the truth.

Q9 — b. 7 % 2 == 0 is false → the else-branch of the conditional operator: 7·3+1 = 22. This line is also the Collatz step — the loop around it comes in Week 5.

Q10 — b. In an else-if chain each test inherits all earlier failures. Reaching the third branch guarantees m ≥ 70, so m < 70 is false forever — a duplicate-condition bug that silently deletes a grade band.

Next: W05–W08 — Control flow and functions → · Hub