Mithat Konar
with material from Capron's “Essentials of Computing”, 2/e

• programming: the discipline of creating computer software.
• computer program:
  • a set of step-by-step instructions
  • that directs the computer to do the tasks you want it to do
  • and produce the results you want.
• Programmer → computer program → software.

• “Write programs”
  • Prepare the instructions of a computer program.
  • Test and correct programs.
  • Document the way a program works.
  • Interact with other programmers, systems analysts, clients.

• programming language:
  • a set of rules used to write computer programs.
  • a way of telling the computer what operations to perform.
• Computers are binary machines.
  • Use only ON/OFF switches to control internal states
  • Only understand instructions that are expressed in ON/OFF (or 1/0) terms.
• To make it easier for humans to program computers, various programming languages have been invented.

• Programming languages exist on a spectrum of low to high level.
  • low level: close to the 1/0 language the computer directly uses.
  • high level: closer to natural language or mathematics.
• Five levels:
  • machine language
  • assembly languages
  • high level languages
  • very high level languages
  • natural language programming

• The lowest level of language.
• Consists of 1’s and 0’s.

10110110100100101101011101001010
10110110110101101101011011000111

• Each type of computer processor has its own machine language.

• Use alphanumeric abbreviations or mnemonic codes as substitutes for machine language
  • ADD for Add, CMP for Compare, MOV for Move, etc.

MOV AL, 1h
MOV CL, 2h
MOV DL, 3h

• An assembler program converts an assembly language program into machine language.

• Use general notation systems that most humans can understand.
  • Often English-like or math-like.
• Much more convenient to write and repair.
• Allows programmer to think less about language details and more about solving problem.
• “Write once, run anywhere.”

• Try to come closer to natural language than high-level languages.

• Tries to let people program using everyday language.
• “Show a list of names from the contact list,” works just as well as “Display the names of everyone in the contact list.”

• High-level languages need to be translated into machine language.
• Three approaches to translation:
  • interpreted: translate one line of the program, run it, move to the next.
  • compiled: translate the whole program at once; produces a machine code file that is executed.
  • hybrid: translate the whole program into an in-between language; execute the in-between language in an interpreter.

• syntax error: you broke a language rule.
• semantic or logic error: the program runs and doesn't complain, but it doesn't produce the desired result.
• runtime error: you ask the program to do something it can't, like divide A by B when B happens to be zero.

1. Define the problem.
2. Design a solution.
3. Code the solution.
4. Test the solution.
5. Document the solution.

• Undefined problems cannot be solved.
• May be formal or informal.
• Sometimes simple, often not.

• Design your solution before you try to build it!
• 80/20 rule: spend 80% of your time designing, 20% writing.

• Write the programming language statements and other resources you need to implement the design.

• debugging: detecting, locating, and fixing mistakes.
• desk checking: working through your code without running it to find mistakes.

• documentation: a written detailed description of the programming cycle and specific facts about the program.
• Many languages let you include some documentation in the program code.
• Documentation is needed:
  • to help organize program planning
  • to help communicate with others about your program.
  • to help remind you what your program is doing.
• Very important!!!

• code editor: used to write the program code (i.e., source code).
• translator: used to translate source code into a form the computer can execute.
• debugger: used to interactively run a program and observe its internal state.
• project manager: used to organize source code and other files associated with a program.
• IDE (integrated development environment): integrates a number of these tools into one unified environment to help increase productivity.

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