Programming Concepts

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Variables & Constants

A variable is an identifier that can change during program execution; declared with `DECLARE <id> : <datatype>` in pseudocode.
Identifiers should use PascalCase, contain only letters/digits, and start with a capital letter.
A constant is an identifier set once; named in UPPERCASE to improve readability and maintainability.
Constants are declared with `CONSTANT <id> ← <value>`; changing a constant only requires alteration in one place.

Data Types

Basic data types: Integer (whole numbers), Real (decimal), Character (single char), String (sequence of chars), Boolean (True/False).
Choosing the correct data type ensures accuracy and efficiency; casting converts between types.
Pseudocode examples: `DECLARE Age : INTEGER`, `DECLARE Price : REAL`, `DECLARE GameOver : BOOLEAN`.

Input & Output

Input reads data from an input device (e.g., keyboard) using `INPUT <identifier>` in pseudocode.
Output sends data to an output device (e.g., monitor) using `OUTPUT <identifier(s)>`.
Without input, programs cannot interact with the outside world; without output, results cannot be seen.

Sequence

Sequence means lines of code run one at a time in the order they are written.
Incorrect sequence can cause unexpected behaviour or runtime errors (e.g., returning a variable before it is assigned).

Selection

Selection changes program flow based on conditions; uses `IF...THEN...ELSE` or `CASE` statements.
`IF` statements: `IF <condition> THEN <statements> ELSE <statements> ENDIF`.
Nested selection places one IF inside another; CASE compares multiple values of the same variable.
Boolean operators `AND`, `OR`, `NOT` combine conditions; `AND` true if both true, `OR` true if at least one true, `NOT` inverts.

Iteration

Count-controlled loops repeat a fixed number of times using `FOR <id> ← <start> TO <end> [STEP <inc>]`.
Condition-controlled loops repeat until a condition is met: `WHILE` (pre-condition) or `REPEAT...UNTIL` (post-condition).
Nested iteration is a loop inside another loop, e.g., a FOR inside another FOR.

Totalling & Counting

Totalling adds up values in a loop: initialise total to 0, then update inside loop.
Counting tracks occurrences: initialise count to 0, increment when condition met.
Both are commonly used with loops to accumulate results.

String Handling

Case conversion: `UCASE`/`LCASE` (pseudocode) or `.upper()`/`.lower()` (Python).
Length: `LENGTH(string)` (pseudocode) or `len(string)` (Python).
Substring: `SUBSTRING(string, start, length)` in pseudocode (start at 1); Python uses slicing `string[start:end]` (start at 0).

Arithmetic, Logical & Boolean Operators

Arithmetic operators: `+`, `-`, `×`, `/`, `MOD` (remainder), `DIV` (quotient), `^` (exponent).
Logical operators compare values: `==`, `<>`, `<`, `≤`, `>`, `≥`.
Boolean operators: `AND`, `OR`, `NOT` used to combine conditions.

Procedures & Functions

Procedures do not return a value; defined with `PROCEDURE ... ENDPROCEDURE` and called with `CALL`.
Functions return a value; defined with `FUNCTION ... RETURNS <type> ... ENDFUNCTION` and called in expressions.
Parameters pass data into sub-programs; multiple parameters allowed.
Sub-programs improve readability, maintainability, and avoid code duplication.

Local & Global Variables

Local variables declared inside a sub-program; only accessible there; destroyed when the sub-program ends.
Global variables declared at the outermost level; accessible from anywhere in the program.
Use local variables to avoid unintended side-effects; global variables can be modified by any part of the program.

Library Routines

Library routines are pre-written, reusable code (e.g., `RANDOM`, `ROUND`) that save time and are already tested.
`RANDOM` generates random numbers; in pseudocode `RANDOM(lower, upper)`; in Python `import random; random.randint(a,b)`.
`ROUND` rounds a number to a specified number of decimal places: `ROUND(value, places)`.

Maintaining Programs

Use layout, indentation, comments, meaningful variable names, white space, and sub-programs to make code easy to maintain.
Consistent use of these techniques improves readability and reduces errors when modifying code.

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Câu hỏi luyện tập

Xem trước miễn phí — 8 trên 54 câu hỏi. Đăng ký để xem tất cả.

1.Which of the following is the correct way to declare a variable in pseudocode?
Easy
- ADECLARE Age : INTEGER
- BDECLARE Age = INTEGER
- CAge : INTEGER
- DINTEGER Age
2.Which data type would be most appropriate to store the value 'True'?
Easy
- ABOOLEAN
- BSTRING
- CINTEGER
- DCHAR
3.What is the output of the following pseudocode? Total ← 0 FOR X ← 1 TO 3 Total ← Total + X NEXT X OUTPUT Total
Medium
- A6
- B3
- C1
- D0
4.Which of the following correctly represents a condition-controlled loop in pseudocode?
Medium
- AWHILE Colour ≠ 'Red' DO INPUT Colour ENDWHILE
- BFOR X ← 1 TO 10 OUTPUT X NEXT X
- CREPEAT INPUT Colour UNTIL Colour = 'Red'
- DIF Colour = 'Red' THEN OUTPUT 'Stop' ENDIF
5.What is the value of Result after executing the following pseudocode? Result ← 10 MOD 3
Easy
- A1
- B3
- C0
- D10
6.Which of the following is a valid constant declaration in pseudocode?
Easy
- ACONSTANT π ← 3.142
- BCONSTANT π = 3.142
- CDECLARE π : CONSTANT ← 3.142
- Dπ CONSTANT ← 3.142
7.What is the purpose of a procedure in programming?
Easy
- ATo perform a task without returning a value
- BTo return a value
- CTo store data permanently
- DTo handle user input
8.Which of the following is the correct pseudocode to output the length of a string stored in variable Word?
Easy
- AOUTPUT LENGTH(Word)
- BOUTPUT LEN(Word)
- COUTPUT Word.LENGTH
- DOUTPUT LENGTH Word

Thêm câu hỏi

9.What is the output of the following pseudocode? Word ← 'Revision' OUTPUT SUBSTRING(Word, 1, 3)
Medium
- ARev
- Bvis
- CRevi
- DRevision
10.Which Boolean operator returns True only when both conditions are True?
Easy
- AAND
- BOR
- CNOT
- DXOR
11.What is the value of Result after executing the following pseudocode? Result ← 17 DIV 4
Easy
- A4
- B1
- C4.25
- D5
12.Which of the following is a library routine used to generate random numbers in Python?
Easy
- Arandom.randint()
- Brandom.randomint()
- Crandint()
- Drandom.int()
13.A program uses a variable 'Total' to add up prices entered by the user. Initially, Total is set to 0. Which of the following correctly updates Total inside a loop that runs 10 times?
Medium
- ATotal ← Total + Price
- BTotal ← Price + 1
- CTotal ← Total + 1
- DTotal ← Price
14.What is the value of 'Result' after the following pseudocode is executed? Result ← 0 FOR X ← 1 TO 4 Result ← Result + X×2 NEXT X
Medium
- A20
- B10
- C16
- D12
15.The following pseudocode uses a function. What is the output? FUNCTION Calc(N: INTEGER) RETURNS INTEGER IF N = 0 THEN RETURN 1 ELSE RETURN N×Calc(N - 1) ENDIF ENDFUNCTION OUTPUT Calc(3)
Hard
- A6
- B3
- C9
- D1
16.Which of the following is the correct pseudocode to check if the variable 'Age' is between 13 and 19 inclusive?
Medium
- AIF Age ≥ 13 AND Age ≤ 19 THEN
- BIF Age > 13 AND Age < 19 THEN
- CIF Age ≥ 13 OR Age ≤ 19 THEN
- DIF Age = 13 TO 19 THEN
17.A program uses a WHILE loop to read temperatures until a value of -1 is entered. Which pseudocode correctly implements this?
Medium
- AINPUT Temperature WHILE Temperature <> -1 DO PROCESS Temperature INPUT Temperature ENDWHILE
- BWHILE Temperature <> -1 DO INPUT Temperature PROCESS Temperature ENDWHILE
- CREPEAT INPUT Temperature PROCESS Temperature UNTIL Temperature = -1
- DFOR X ← 1 TO 100 INPUT Temperature IF Temperature = -1 THEN EXIT PROCESS Temperature NEXT X
18.The table shows the results of a survey. Which pseudocode correctly calculates the total number of people who chose 'Yes'? Response: Yes, No, Yes, Yes, No, Yes
Medium
- ACount ← 0 FOR Each Response IF Response = 'Yes' THEN Count ← Count + 1 ENDIF NEXT OUTPUT Count
- BCount ← 0 FOR Each Response Count ← Count + 1 NEXT OUTPUT Count
- CTotal ← 0 FOR Each Response IF Response = 'Yes' THEN Total ← Total + Response ENDIF NEXT OUTPUT Total
- DCount ← 1 FOR Each Response IF Response = 'Yes' THEN Count ← Count + 1 ENDIF NEXT OUTPUT Count
19.What is the purpose of the DIV operator in pseudocode?
Easy
- AIt returns the integer part of a division (quotient)
- BIt returns the remainder of a division
- CIt performs floating-point division
- DIt multiplies two numbers
20.What is the output of the following pseudocode? Word ← 'Computer' OUTPUT SUBSTRING(Word, 4, 3)
Medium
- Aput
- Bomp
- Cute
- DCom
21.A program uses the following pseudocode. What is the value of 'Total' after execution? Total ← 0 FOR X ← 1 TO 3 FOR Y ← 1 TO 2 Total ← Total + X×Y NEXT Y NEXT X
Medium
- A18
- B12
- C24
- D36
22.Which of the following is a valid declaration of a constant in pseudocode?
Easy
- ACONSTANT π ← 3.142
- BCONSTANT π = 3.142
- Cπ ← 3.142
- DDECLARE π : CONSTANT ← 3.142
23.What is the most appropriate data type for storing a person's name?
Easy
- ASTRING
- BCHAR
- CREAL
- DBOOLEAN
24.The following pseudocode is intended to output the largest of three numbers. Which line contains an error? 01 INPUT A 02 INPUT B 03 INPUT C 04 IF A > B THEN 05 IF A > C THEN 06 OUTPUT A 07 ELSE 08 OUTPUT B 09 ENDIF 10 ELSE 11 IF B > C THEN 12 OUTPUT B 13 ELSE 14 OUTPUT C 15 ENDIF 16 ENDIF
Hard
- ALine 08
- BLine 04
- CLine 11
- DLine 14
25.A program uses a variable 'Count' to count how many numbers entered by the user are greater than 10. The program inputs 20 numbers. Which pseudocode correctly implements this?
Medium
- ACount ← 0 FOR X ← 1 TO 20 INPUT Num IF Num > 10 THEN Count ← Count + 1 ENDIF NEXT X OUTPUT Count
- BCount ← 0 FOR X ← 1 TO 20 INPUT Num IF Num > 10 THEN Count ← Count + Num ENDIF NEXT X OUTPUT Count
- CCount ← 0 FOR X ← 1 TO 20 INPUT Num IF Num > 10 THEN Count ← Count + 1 ENDIF OUTPUT Count NEXT X
- DCount ← 1 FOR X ← 1 TO 20 INPUT Num IF Num > 10 THEN Count ← Count + 1 ENDIF NEXT X OUTPUT Count
26.What is the output of the following pseudocode? Total ← 0 FOR X ← 1 TO 4 FOR Y ← 1 TO X Total ← Total + Y NEXT Y NEXT X OUTPUT Total
Medium
- A20
- B10
- C30
- D15
27.Which of the following is the correct pseudocode to declare a constant for the value of VAT (20%)?
Easy
- ACONSTANT VAT ← 20
- BCONSTANT VAT = 20
- CDECLARE VAT : CONSTANT ← 20
- DVAT ← 20
28.What is the value of Result after executing the following pseudocode? Result ← 0 FOR X ← 1 TO 5 IF X MOD 2 = 0 THEN Result ← Result + X ENDIF NEXT X
Medium
- A6
- B9
- C15
- D0
29.Which of the following correctly describes the difference between a function and a procedure?
Easy
- AA function returns a value; a procedure does not.
- BA procedure returns a value; a function does not.
- CA function can only be called once; a procedure can be called multiple times.
- DA procedure can take parameters; a function cannot.
30.A program contains the following pseudocode: FUNCTION Check(N : INTEGER) RETURNS BOOLEAN IF N < 0 THEN RETURN True ELSE RETURN False ENDIF ENDFUNCTION What is the output of: OUTPUT Check(5 - 7)
Medium
- ATrue
- BFalse
- C5
- DError
31.Which data type should be used to store the value 'a'?
Easy
- ACHAR
- BSTRING
- CINTEGER
- DBOOLEAN
32.What is the output of the following pseudocode? Word ← 'Programming' OUTPUT SUBSTRING(Word, 5, 4)
Medium
- Agram
- Bramm
- CProg
- Dming
33.A program uses the following pseudocode to calculate the average of numbers entered. The user enters numbers until they enter 0. Which pseudocode correctly implements this?
Hard
- ATotal ← 0 Count ← 0 INPUT Num WHILE Num <> 0 DO Total ← Total + Num Count ← Count + 1 INPUT Num ENDWHILE IF Count > 0 THEN OUTPUT Total / Count ENDIF
- BTotal ← 0 Count ← 0 INPUT Num WHILE Num <> 0 DO Total ← Total + Num Count ← Count + 1 ENDWHILE OUTPUT Total / Count
- CTotal ← 0 Count ← 0 INPUT Num WHILE Num <> 0 DO Total ← Total + Num INPUT Num Count ← Count + 1 ENDWHILE OUTPUT Total / Count
- DTotal ← 0 Count ← 0 REPEAT INPUT Num Total ← Total + Num Count ← Count + 1 UNTIL Num = 0 OUTPUT Total / Count
34.Which Boolean operator returns True only when both conditions are False?
Medium
- ANOT (A OR B)
- BA AND B
- CA OR B
- DNOT A AND NOT B
35.What is the value of Result after executing the following pseudocode? Result ← 27 DIV 4
Easy
- A6
- B7
- C3
- D6.75
36.Which of the following pseudocode statements correctly generates a random integer between 10 and 20 inclusive?
Medium
- ARANDOM(10, 20)
- BRANDOM(10, 21)
- CRANDOM()×10 + 10
- DROUND(RANDOM()×10 + 10, 0)
37.Which of the following is the correct pseudocode to declare a constant named π with value 3.142?
Easy
- ACONSTANT π ← 3.142
- BDECLARE π : REAL ← 3.142
- Cπ ← 3.142
- DCONSTANT π = 3.142
38.Which of the following data types would be most appropriate to store the value 'True'?
Easy
- AINTEGER
- BBOOLEAN
- CSTRING
- DCHAR
39.What is the output of the following pseudocode? X ← 5 Y ← 10 IF X > Y THEN OUTPUT X ELSE OUTPUT Y ENDIF
Easy
- A5
- B10
- CX
- DY
40.What is the value of Result after executing the following pseudocode? Result ← 0 FOR X ← 1 TO 4 Result ← Result + X NEXT X
Easy
- A4
- B10
- C16
- D24
41.Which of the following is the correct pseudocode to declare a constant named VAT with a value of 20?
Easy
- ACONSTANT VAT ← 20
- BCONSTANT VAT = 20
- CVAT ← 20
- DDECLARE VAT : CONSTANT ← 20
42.Which data type would be most appropriate to store the value 3.14?
Easy
- AINTEGER
- BREAL
- CSTRING
- DBOOLEAN
43.In pseudocode, the keyword OUTPUT is used to display data on the screen.
Easy
True or false?
44.What is the output of the following pseudocode? X ← 1 WHILE X < 4 DO OUTPUT X X ← X + 1 ENDWHILE
Easy
- A1 2 3
- B1 2 3 4
- C2 3 4
- D0 1 2 3
45.Which of the following correctly calculates the total of numbers entered by a user? The user enters numbers until they enter -1.
Medium
- ATotal ← 0 INPUT Num WHILE Num <> -1 DO Total ← Total + Num INPUT Num ENDWHILE
- BTotal ← 0 REPEAT INPUT Num Total ← Total + Num UNTIL Num = -1
- CTotal ← 0 WHILE Num <> -1 DO Total ← Total + Num ENDWHILE
- DTotal ← 0 FOR X ← 1 TO 10 INPUT Num Total ← Total + Num NEXT X
46.What is the output of the following pseudocode? Word ← 'Programming' OUTPUT SUBSTRING(Word, 1, 4)
Easy
- AProg
- Bgram
- CPro
- DP
47.In pseudocode, the MOD operator returns the quotient of integer division.
Easy
True or false?
48.What is the value of Result after executing the following pseudocode? Result ← 0 FOR X ← 1 TO 3 FOR Y ← 1 TO X Result ← Result + Y NEXT Y NEXT X
Medium
- A10
- B6
- C14
- D8
49.Match each pseudocode operator with its description.
Medium
- DIV
- MOD
- ^
- Exponentiation
- Quotient of integer division
- Remainder of integer division
50.Arrange the following pseudocode lines in the correct order to input three numbers and output the largest.
Hard
- IF A ≥ B AND A ≥ C THEN
- OUTPUT A
- ELSE IF B ≥ A AND B ≥ C THEN
- OUTPUT B
- ELSE
- OUTPUT C
- ENDIF
- INPUT A
- INPUT B
- INPUT C
51.Complete the pseudocode to count how many numbers from 1 to 10 are greater than 5.
Easy
Count ← 0 FOR X ← 1 TO 10 IF X ____ 5 THEN Count ← Count + 1 ENDIF NEXT X
52.What is the length of the string 'Computer Science'?
Easy
53.Name the Boolean operator that returns True only when both conditions are True.
Easy
54.What is the length of the string 'Computer Science'?
Easy
- A15
- B18
- C16
- D17

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