Variables, data types and operators

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Notes de leçon Diapos Questions d'entraînement

Notes de leçon

Variables and constants

A variable is a named memory location whose value can change. A constant has a value that does not change while the program runs (e.g. VAT rate).
Assignment stores a value: score = 10. Use meaningful names (e.g. totalCost) and consistent style.

Variables and constants

Data types

Integer (whole numbers), real (numeric values that can include a fractional part; an integer-valued number can also be stored using a real type). Floating-point is a finite representation and may involve rounding, Boolean (True/False), character (a single symbol), string (text).
Casting converts between types: converting the string "12" to integer 12, or 7 to the string "7".

Choosing a data type

Operators

Arithmetic: + - * / MOD (remainder) DIV (integer division) ^ (exponent). Example: 17 MOD 5 = 2; 17 DIV 5 = 3.
Comparison: = (or ==), ≠, <, >, ≤, ≥.
Boolean: AND, OR, NOT.

Operators

Input and output

INPUT reads data (usually a string, then cast); OUTPUT or print displays data.

Order of operations

Brackets first, then exponents, multiplication and division, then addition and subtraction.

Good practice

Declare variables, choose appropriate types, and comment code.

Diapos

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Questions d'entraînement

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1.What is a variable?
Easy
- Aa named stored value that can be updated
- Ba value that is always fixed
- Ca repetition instruction
- Da syntax error
2.What is a constant?
Easy
- Aa value that does not change
- Ba value that changes
- Ca loop
- Da function
3.Which data type is intended specifically for whole-number values?
Easy
- Ainteger
- Bstring
- CBoolean
- Dreal
4.Which data type stores text?
Easy
- Astring
- Binteger
- CBoolean
- Dreal
5.Which data type stores True or False?
Easy
- ABoolean
- Binteger
- Cstring
- Dreal
6.What is 17 DIV 5?
Easy
- A3
- B2
- C3.4
- D12
7.What is 20 MOD 6?
Easy
- A2
- B3
- C14
- D6
8.What is the value of 2 + 3×4?
Easy
- A14
- B20
- C24
- D10

Plus de questions

9.What does casting do?
Easy
- Achanges the data type of a value
- Bdeletes a value
- Ccompresses data
- Drepeats code
10.Which listed type is most suitable for a person’s age recorded in completed years?
Easy
- Ainteger
- Bstring
- CBoolean
- Dreal
11.Which of the listed types can represent a fractional numeric value such as 4.99?
Easy
- Areal
- Binteger
- CBoolean
- Dcharacter
12.What is the output of: a = 3 b = a×2 OUTPUT b + 1
Medium
- A7
- B6
- C5
- D9
13.What is the result of "5" + "3" if both are strings and + joins?
Medium
- A53
- B8
- C5 3
- Derror
14.What is the result of 5 + 3 if both are integers?
Medium
- A8
- B53
- C15
- Derror
15.Which is a valid Boolean expression?
Medium
- Ax > 5 AND x < 10
- Bx + 5
- C"hello"
- D42
16.What does NOT True give?
Medium
- AFalse
- BTrue
- Cthe string "True"
- Da syntax error
17.What does True AND False give?
Medium
- AFalse
- BTrue
- C1
- Derror
18.What does True OR False give?
Medium
- ATrue
- BFalse
- C0
- Derror
19.What is the output? x = 7 y = x MOD 3 OUTPUT y×x
Medium
- A7
- B21
- C3
- D10
20.A program stores the user's input "25" as a string. What is needed before adding 5?
Medium
- Acast it to an integer
- Bdelete it
- Ccompress it
- Dleave it
21.Which variable name best describes the total price of a purchase?
Medium
- AtotalCost
- Bx1
- Ca
- Dthing
22.Why use constants?
Medium
- Ato avoid accidentally changing a fixed value
- Bto use more memory
- Cto speed hardware
- Dto hide code
23.What does = do in an assignment?
Easy
- Astores a value in a variable
- Bcompares values
- Cends a line
- Dadds
24.What does ≤ mean?
Easy
- Aless than or equal to
- Bgreater than
- Cnot equal
- Dequal
25.What does ≠ mean?
Medium
- Anot equal to
- Bequal to
- Cgreater than
- Dless than
26.Which operator gives the remainder?
Medium
- AMOD
- BDIV
- C*
- D+
27.A variable's value can change.
Easy
True or false?
28.A string can store text.
Easy
True or false?
29.17 MOD 5 equals 3.
Easy
True or false?
30.Casting converts data from one type to another.
Easy
True or false?
31.A constant changes while the program runs.
Medium
True or false?
32.Which are data types?
Medium
- Ainteger
- Bstring
- CBoolean
- Dreal
- Eloop
33.Which are arithmetic operators?
Medium
- A+
- B-
- CMOD
- DDIV
- EAND
34.Write pseudocode to store the length and width of a rectangle and output its area.
Medium

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