Sequences and Sequencing
A program consists of a sequence of instructions that tells the computer exactly what to do.
Sequencing refers to writing instructions in a structured and ordered manner.
Définition
What is a Computer Program?
A program is a sequence of instructions that tells a computer what to do to solve a problem.
Programs can be used for different types of computations:
Mathematical (e.g., calculating the square root of a number)
Statistical (e.g., performing regression analysis)
Symbolic (e.g., searching and replacing text in a document)
Graphical (e.g., playing a video or processing an image).
A program consists of input, output, processing, and optional conditional execution or repetition.
Définition
What is a Sequence?
A sequence is a structured set of ordered steps that explicitly solve a problem.
It reflects manual processes and business rules related to a specific problem domain.
Sequences are not generalizable; they are specific to a task.
Later, we can learn to abstract sequences into reusable algorithms.
Writing Code: Input, Output, and Processing
Input and Output
- Input: Data received by the computer (from users, files, sensors, etc.).
- Output: Data sent back by the program (displayed on screen, saved to a file, printed, etc.).
- Inputs and outputs can be stored for later use.
Processing
- Processing transforms input into output.
- It includes basic mathematical and statistical operations (addition, subtraction, averages, percentages, etc.).
Writing Output to the Screen
- The
print()function in Python is used to display output on the screen. - Example:
print("Hello, World!")
Adding Pseudo-code
- Pseudo-code consists of comments that describe what the code does.
- In Python, comments start with
#and are ignored by the interpreter. - Helps make complex code more understandable.
Operands, Operators, and Operations
Basic Arithmetic Operations
- Operators: Used to perform operations on values (operands).
- Common mathematical operators in programming:
+Addition-Subtraction*Multiplication/Division%Modulo (remainder after division)//Integer division (rounds down the result)
Order of Operations (Precedence)
- Parentheses (highest precedence) →
(3+2) * 5 - Exponentiation →
2**3(2 raised to the power of 3) - Multiplication and Division → Evaluated before addition/subtraction
- Left-to-right evaluation when operators have the same precedence
5. Debugging: Fixing Errors and Bugs
Common Types of Errors in Programming
- Syntax Errors: Mistakes in code structure (e.g., missing parentheses or colons).
- Semantic Errors: Code runs but produces incorrect results due to logic mistakes.
- Runtime Errors: Unexpected issues that cause the program to crash (e.g., division by zero).
Debugging Strategies
- Carefully read error messages to locate the issue.
- Use print statements to track variable values.
- Write comments to document complex parts of the code.
