1. C++ Introduction

Today’s Outline

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• What’s a computer
• Programming languages
• Basics of computer programming

What’s a computer

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Arithmetic Circuits

Stored Program Computer

Instruction

• A sequence of bits that defines a single operation of a CPU
  • e.g. add, sub, read, write

Instruction Set Architecture, ISA

• ISA is the specification of instructions supported by a CPU
  • The dictionary of CPU language
  • e.g. x86, RISC, …
• ISA is the interface between HW and SW
  • Different CPUs can run the same computer program as long as they support the same ISA

Programming Languages

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Machine Language

• A language that is directly understood by the computer.
• Defined by ISA such as x86, RISC, …

Symbolic Language

• English-like abbreviations representing elementary computer operations.
• e.g. Assembly language

High-level Language

• Close to human language.
• e.g. C/C++, Java, Python, …

Compiler

• Computers only understand binary code
• Humans write programs using a high-level language
• The compiler translates high-level language programs to binary code

Compiled Languages

• Compiled language programs are compiled to binary machine code, which is then directly executed by the HW
• e.g. C/C++, Rust, Pascal, …
• Pros - fast
• Cons - need to re-compile on a different HW

Interpreted Languages

• Programs are first compiled to an Intermediate Representation, IR, which is then converted by a Virtual Machine, VM to machine code and executed by the HW
• e.g. Java, Python, …
• Pros - better portability
• Cons - slow

Basics of Computer Programming

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Computer Program (External View)

• Basic elements of a computer program
  • Input
  • Process
  • Output

Computer Program (Internal View)

• A list of instructions ordered logically
• Usually, involve data access

Developing a C++ Program

1. Coding
   • Write source code into a file
   • e.g. hello.cpp
2. Compile
   • Source code is converted to object code in machine language
   • e.g. hello.obj
3. Link
   • Combines objects and libraries to create a binary executable
   • e.g. hello.exe

Function

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ReturnType FunctionName(input parameters)
{
    instructions within function body
}

• A sequence of instructions grouped together, which implement a specific task.

main()

• main() is a special function, which is the starting point of a C++ program.

Statement

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cout << "Hello world!" << endl;

• A syntactic unit that expresses some action to be carried out.

cout

• An output function provided by iostream library
• cout
  • Console Output allows our program to output values to the standard output stream
• <<
  • output operator, which output values to an output device
  • The right-hand side of the << is the string to output
• endl
  • end of the line. advance the cursor on the screen to the beginning of the next line

#include

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#include <iostream>
using namespace std;
 
void main()
{
    cout << "Hello world!" << endl;
}

• Include the libraries you want to use
• e.g. iostream commonly used functions for I/O, including cout
• e.g. cmath commonly used math functions, such as sin() cos() log()

using namespace

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#include <iostream>
using namespace std;
 
void main()
{
    cout << "Hello world!" << endl;
}

• namespace
  • A declarative region that provides a scope to the identifiers inside it
  • Declare namespace to avoid writing the full name
• e.g. std namespace is used such that we can write cout instead of std::cout

Summary

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What’s Computer

• Numbering System
• Logic gates and circuits
• Stored Program Computer and ISA

Programming Language

• Machine / Symbolic / High-level Language
• Compiler

Basics of Computer Programming

• Logic Flow
• Developing: Coding / Compilation / Linking
• C++ Syntax: Function / Statement / …