1. Introduction to computer software

2. Programming the computer Program, is a sequence of instructions, written to perform a specified task on a computer Source code is a program written in a programming language. A programming language is a formal constructed language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs to control the behavior of a machine or to express algorithms. Object code, is what a computer compiler produces In a general sense object code is a sequence of statements or instructions in a computer language, usually a machine code language (i.e., binary).

3. Programming the computer Initially, a programmer writes a program in a particular programming language. This form of the program is called the source program, or more generically, source code. To execute the program, however, the programmer must translate it into machine language, the language that the computer understands. The first step of this translation process is usually performed by a utility called a compiler. The compiler translates the source code into a form called object code. Sometimes the object code is the same as machine code; sometimes it needs to be translated into machine language by a utility called an assembler.

4. Programming Languages Machine Language Assembly Language High level Language

5. Machine Language In the earliest days of computers, the only programming languages available were machine languages. Each computer had its own machine language, which was made of streams of 0s and 1s. The fundamental language of the computer ’ s processor, also called Low Level Language. All programs are converted into machine language before they can be executed. Consists of combination of 0 ’ s and 1 ’ s that represent high and low electrical voltage.

6. Assembly Language The next evolution in programming came with the idea of replacing binary code for instruction and addresses with symbols or mnemonics. Because they used symbols, these languages were first known as symbolic languages. The set of these mnemonic languages were later referred to as assembly languages.

7. Assemblers, Loaders Assembeler Converts assembly language programs into object files. Assembeler translates assembly instructions and pseudo-instructions into machine instructions – Convert decimal numbers, etc. specified by programmer into binary. Loader: Loader is a program that loads machine codes of a program into the system memory.

8. High Level Language Although assembly languages greatly improved programming efficiency, they still required programmers to concentrate on the hardware they were using. Working with symbolic languages was also very tedious, because each machine instruction had to be individually coded. The desire to improve programmer efficiency and to change the focus from the computer to the problem being solved led to the development of high-level languages. Computer (programming) languages that are easier to learn. Uses English like statements. Examples are C ++, Visual Basic, Pascal, Fortran and …....

9. Compilers and interpreters Compiler: During compilation the entire program is converted into executable OBJECT code. It can be saved and reloaded several times. This is especially useful for larger programs that have to be executed several times without having to be modified. Interpreter: The source code is translated by the interpreter instruction by instruction into machine language and immediately executed. At every execution the translation is redone. This is interesting to debug programs or for small programs using little mass memory. Source code takes much less space than object code.

10. Compilers and Interpreters Source code CompilerInterpreter Object code Hardware

11. Advantages and Disadvantages of high- level and low-level languages High level languages are portable Low level languages take less memory therefore they are faster.

12. Opcode & Operand Opcode is the portion of a machine language instruction that specifies the operation to be performed. What to do and How to do it. operand is the part of a computer instruction that specifies data that is to be operating on or manipulated and, by extension, the data itself.

13. HC11 Memory addressing Inherent Immediate Extended Direct Indexed Relative

14. Machine cycles Fetch - Retrieve an instruction from the memory. Decode - Translate the retrieved instruction into a series of computer commands. Execute - Execute the computer commands. Store - Sand and write the results back in memory.

15. HC11 Four step Machine Cycle

16. Flowchart Symbols

17. Flowchart example

18. Problems Chapter questions. Pages 49,50 Problems 3,4,5,6,7,9,10,11,15,20,22,23 Chapter Problems. Page 50 Problems 1, 2