Introduction to Computers and Programming #
What is a Computer? #
Electronic device that proccess data by following a set of instructions (= program). It can perform calculations, store and retrieve information and controlls devices.
Von Neumann Architecture #
Proposed by John von Neumann in 1945.
Input devices #
Serve to enter data and instructions. Analogy: like your senses - they gather information for the computer from the outside worlds. Examples:
- Keyboard
- Mouse
- Microphone
- Scanner
- Touch display
Output devices #
Present results of computer’s processing to the user. Examples:
- Monitor
- Printers
- Speakers
Analogy: your actions. You communicate with (towards) the world by them.
How does a CPU work? #
- Control Unit (CU): The Brain of the computer. Control Unit directs flow between memory, CPU, I/O devices
- Arithmetic Logic Unit (ALU): performs arithmetic (+, -, …) and logical operations (AND, OR).
Logical operations are also called boolean operations after
George Boole. True is often represented as 1 and False as 0.
Logical AND #
| Input A | Input B | A ∧ B |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
Logical OR #
| Input A | Input B | A ∨ B |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
Memory and Storage #
Registers #
- Registers are small, high-speed storage locations within the CPU itself.
- Extremely fast (much faster than memory or storage).
- Very limited in size (typically 8, 16, 32, or 64 bits wide, depending on the CPU architecture).
- Registers fetch instructions from memory, store intermediate computation results, and provide operands for the CPU.
RAM #
- Memory is the part of the system used for temporarily storing data and instructions that the CPU needs during program execution.
- It acts as the workspace for active processes and provides data to the CPU.
- Stores instructions fetched from storage so that they can be quickly accessed.
- Slower than registers but faster than storage.
- Larger in size compared to registers (e.g., modern systems have several GBs of RAM).
- Volatile: contents are lost when power is turned off.
- The CPU reads instructions and data from memory into registers. Once a task is complete, results may be written back to memory.
Storage #
- Storage refers to non-volatile devices, such as hard drives (HDDs), solid-state drives (SSDs), or even cloud storage (e.g. AWS S3).
- Long-term retention of data and programs, even when the computer is turned off.
- Much slower than both memory and registers.
- Much larger capacity compared to memory and registers (e.g., modern systems often have TBs of storage).
Operating Systems #
An Operating System (OS) is software that manages a computer’s hardware and software resources, acting as an intermediary between users and the computer hardware. It ensures efficient execution of programs, resource allocation, and system stability.
Functions #
- Process Management
- Memory Management
- File System Management
- Device Management
- User Interface
Types #
- Windows
- UNIX
- Linux
- Android
- macOS
- iOS
- Linux
Programming Languages #
Programming languages are the medium for humans to write programs that a computer can execute. They are needed to:
- Bridge the gap: Computers understand only binary (0 and 1). Computer languages allow for writing instructions in a human readable form.
- Simplification : allow to break down problems into
- Resuse: programs can be reused and automate repetitive tasks.
Types #
Low-Level Languages #
- Machine Language: Example:
10110000 01100001 - Assembly langauage: symbolic representation of machine language using mnemonics. Example:
MOV A, 5
ADD B, A
High-Level Languages #
Designed to be easier to read and write, closer to human languages. Requires a compiler or interpreter (or both) to translate into machine code. Examples:
- C: very low-level and thus performant. Compiled. Non-portable.
- Java: First compiled. Then resulting code is interpreted in the Java Virtual Machine. Cross-platform. Popular for enterprise apps.
- JavaScript: Very high level. Leans closer to C-style syntax. Used in browsers to create Frontends.
- Python: Very high level, easy to read, beginner friendly. Cross-platform. Popular for data-science (AI), prototyping and scripting.
High level scripting languages are used for automating tasks. Examples:
- Python
- Bash
Compiled vs. Interpreted #
- Computer only understands machine code
- Some languages compile their files into machine code (e.g. C)
- Some take the source code and interpret it (e.g. Python)
- Some use both approaches (e.g. Java)
Usually low-level (performant) languages are compiled and high-level (closer to human thinking) are interprete.
Common Characteristics #
- Syntax: rules, how code must be written.
- Semantics: Meaning of a statement or instruction. Example:
print("Hello")
2+2
- Control Structures: loops and condititionals that control the flow of exeuction. Example
if,while.
Categories of High-Level Languages #
- Procedural: focus on a sequence of steps to solve a problem. Example: C.
- Object-Oriented: model entities of outside worlds as objects encapsulating data and behavior. Example: Java, C++.
- Functional: focus on mathematical functions. Example: Haskell.
- Logical: express facts and rules for reasoning. Example: Prolog.
Some programming languages fit into several categories, e.g. Python and Javascript support both procedural, object-oriented and functional programming.
Homework (graded) #
htop #
- Install
htop. Don’t know how? Use Google/ChatGPT. - Make a screenshot.
- Identify any process and explain what its values mean.