1.4 Machine Languages, Assembly Languages and High-Level Languages¶

Programmers write instructions in various programming languages
- Some directly understandable by computers
- Others require intermediate translation steps
Three general types
1. Machine languages
2. Assembly languages
3. High-level languages

Machine Languages¶

Any computer understands only its own machine language, defined by its hardware design
Generally consist of strings of numbers (ultimately 1s and 0s) that instruct computers to perform their most elementary operations
Cumbersome for humans
Section of an early machine-language payroll program that adds overtime pay to base pay and stores the result in gross pay
```
+1300042774
+1400593419
+1200274027
```

Assembly Languages and Assemblers¶

English-like abbreviations to represent elementary operations
Formed the basis of assembly languages
Assemblers were developed to convert assembly-language programs to machine language at computer speeds
Section of an assembly-language payroll program that adds overtime pay to base pay and stores the result in gross pay
```
load    basepay
add     overpay
store   grosspay
```

High-Level Languages and Compilers¶

With the advent of assembly languages, computer usage increased rapidly
Programmers still needed numerous instructions to accomplish even simple tasks
High-level languages enable single statements to accomplish substantial tasks
A typical high-level-language program contains many statements, known as the program’s source code

High-Level Languages and Compilers (cont.)¶

Compilers convert high-level-language source code into machine language
High-level languages look almost like everyday English and contain commonly used mathematical notations
Payroll program written in a high-level language might contain a statement such as
```
grossPay = basePay + overTimePay
```
Python is among the world’s most widely used high-level programming languages

Interpreters¶

Interpreter programs execute high-level language programs directly and avoid the delay of compilation
Interpreted programs run slower than compiled programs
Most widely used Python implementation—CPython—uses a clever mixture of compilation and interpretation to run programs

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