What is Programming?

1
What is Programming?

• A program is a list of instructions that is
  executed by a computer to accomplish a particular
  task.
• Creating those instructions is programming by a
  programmer

2

• Programming language
• Special language (like French or German)
• Understood by the computer
• Tells the computer what to do
• Used by a programmer to write a program
• Visual Basic, Java, C, C, COBOL
• Machine language
• Language of the computer
• Every Programmer language is converted to
  machine language
• Consists of bits on or off only
• Compiler or interpreter
• Software that translates programming languages to
  machine language

3

• Coding the program
• Select the programming language
• Write the instructions
• Using software to translate the program into
  machine language
• Programmers write instructions in English-like
  high-level languages
• Compilers or interpreters change the programs
  into low-level machine language that can be
  executed
• Syntax errors are identified by the compiler or
  interpreter

4
Binary Machine Language all data types consist
of 1s and 0s

• 1 bit (0 or 1)
• 4 bits nibble
• 1 byte 8 bits 2 nibbles
• Is the storage for one character
• 1 word 4 bytes
• 1 K 1 KB 1 kilobyte 1,0240 bytes 210
  bytes
• Kilo 1,000 1 KB 1,000 bytes
• 1 Meg 1 megabyte (MB) 1 million 1024 KB
• 1 GB 1 gigabyte (GB) 1024 MB
  1,000,000,000
• Many people approximate to steps of 1000, not
  1024

5
Programming Languages

• Machine Languages
• 0110110111110111 0000000100000000
  0000000100000000
• Assembly Languages
• One programmer instruction converted to 1 machine
  level instruction
• ADD A,B
• High-level Languages
• Looks more like English words and algebraic
  expressions
• Examples of high level languages
• Programmer instruction converted to many machine
  level
• ADA BASIC
• C FORTRAN
• COBOL Java
• Pascal Visual Basic

6
Machine Language Generation
Programmer written computer code
Programmer written computer code
Translator (Interpreter) Program(browser)
Compiler
Assembler
FUNCTIONBrowsersnetscapeMS ExplorerJavascript
PHPASP
Many machine Language Instructions
.exe file
Execute
Execute
MS Word, Windows XP, MS Excel, Vista, MS Explorer
7
Writing Programs

• To write a program in a high-level language, you
  need
• Appropriate software
• A text editor to type and edit program statements
• A debugger to help find errors in program code
• A compiler or interpreter to translate the
  program into machine language

8
Error Types
Syntax the rules governing word usage and
punctuation in the language(format, recipe,
formula)

• Logic errors are more difficult to locate than
  syntax errors

9
Syntax Error Cycle
10

• A program must be free of syntax errors to be
  run, or executed, on a computer
• The program will not compile or be translated
• A message will point out the offending
  instruction
• To function properly, the logic must be correct
• The program will still execute
• The output may be incorrect
• The program may exit prematurely
• The program may ABEND (Abnormal Termination)
• The program may execute with no errors/problems

11
Logic

• A program must be free of syntax errors to be
  run, or executed, on a computer
• To function properly, the logic must be correct
• Whats wrong with this logic for making a cake?

12

• Two major programming techniques
• Procedural programming
• Object-oriented programming
• Procedural programming focuses on the procedures
  that programmers create
• Object-oriented programming focuses on objects
  that represent real-world things and their
  attributes and behaviors
• Both techniques employ reusable program modules

13
Mainline Logical Flow Through a Program
Procedural program one procedure follows another
from beginning to end Mainline logic has three
distinct parts Housekeeping steps to get
ready Main loop instructions executed for every
input record End-of-job steps taken at end of
program Break the logic down into at least three
modules
14
Mainline Logical Flow Through a Program
15
Mainline Logical Flow Through a Program

• Modularization of the program
• Keeps the job manageable
• Allows multiple programmers to work
  simultaneously
• Keeps the program structured

16
Housekeeping Tasks

• Housekeeping tasks include all steps that occur
  at the beginning of the program
• Declare variables
• Open files
• Perform one-time-only tasks such as printing
  headings
• Read the first input record

17
Annotate the Output

• If the output consists of numbers or any data
  that has no explanatory text with it, you should
  annotate your output this means to add some
  text so the user knows what the output means.