1. Programming Languages
Lecture L11.1

2. Programming Hierarchies
Low-level and High-level Programming
Compatibility

3. Programming Hierarchies
Lowest level construct:
Wire signals
Recall from before

4. Programming Hierarchies
Lowest Level Language:
Machine Code
8086 Microprocessor

5. Programming Hierarchies
A Level Higher:
Assembly Language
8086 Microprocessor

6. Programming Hierarchies
A Hierarchy of Programming Languages

7. Programming Hierarchies
Higher level languages – Advantages
Create programs faster
Easier to manage program development in large or small groups
Easier to manage program evolution
Easier to think about program components, i.e. Functions, Objects
Create a layer (compiler) that can compile the same source code to different target microprocessor architectures

8. Programming Hierarchies
Higher level languages – Disadvantages
Code can be less optimized – run slower than if done in assembly
High-level languages are designed for optimally developing different types of software, it’s important to choose the correct one

9. Some High-level Programming Languages

10. A Computer Program Source Code File
Contains the words written by a computer programmer
Object Code File
Usually produced by a compiler
The Source code translated into Machine Code
Executable File (.EXE)
One or more object code files linked together and possibly with one or more library files
Can be executed on the microprocessor
Operating System
Performs basic functions such as tracking files & directories and controlling peripheral devices
Provides a platform on top of which other programs run

11. A Computer Program

12. Compatibility Compatibility
Depends on the machine code for the processor and operating system
Some popular Intel, AMD, Cyrix microprocessors, for example, have compatible machine codes
Executable files can be run on any of these microprocessors (with an operating system)
No recompilation required

13. Compatibility (cont’d)
Other microprocessors don’t have the same machine codes but they do have a C compiler that will compile the source code for their target architecture
Executable files for one microprocessor can not be run directly on the other
Source code files can be recompiled to an object file/executable file that will run on the target microprocessor
Sometimes modifications must be made to the
C program for it to work (usually slight)
Process of modifying is called ‘porting’

14. Compatibility
Not all microprocessors (or microcontrollers) implement enough machine codes to make it worthwhile to develop C (or other) compilers for them.
Some microprocessors have limited assembly
Specific-purpose processors
Processors designed for simple, small tasks
Programming usually is at the assembly level