Programming at a high level

Developing a Computer Program Programmer  Writes program in source code (VB or other language) Compiler  Converts source code to machine language code Linker  Combines machine language with libraries & converts them to an executable module Interpreter  Converts source code to machine language and executes one line at a time CompilerLink/load Executable module Source code Machine language Output Input data High-level language Low-level Language

Model Building Process Problem identification  Important elements to be modeled  Relations and interactions between them  Degree of accuracy Conceptualization and development  Mathematical description  Type of model  Numerical method - computer code  Grid, boundary & initial conditions Calibration  Estimate model parameters  Model outputs compared with actual outputs  Parameters adjusted until the values agree Verification  Independent set of input data used  Results compared with measured outputs

Programming Process Grace M. Hopper First “Bug” Algorithm Design (underlying logic of program) Program Composition Debug & test (error free & reliable) Program Documentation Program Maintenance

Programming Tools Tools to convert algorithms into computer programs Algorithm: Step-by-Step procedure for solving a problem Example Problem: You write a letter. To mail it, you must decide how much postage to put on the envelop. Rule of Thumb: One stamp for every 5 sheets of paper. Algorithm: see next slide

Algorithm 1. Request the number of sheets of paper; call this “Sheets” 2. Divide Sheets by 5 3. Round the quotient up to the next highest whole number; call it “Stamps” 4. Reply with the number Stamps 5. Example: INPUT (16) Processing Output (4)

Flowchart Symbols Flow Line Start/Stop Input/Output Processing Decision

Stamp Problem Program: Determine the proper number of stamps for a letter  Read sheets  Set the number of stamps to sheets/5  Round the number of stamps up to the next whole number  Display the number of stamps Start Read sheets Set stamps = sheets/5 Round stamps up To next whole # Display stamps End Input Processing Output Flowchart Pseudocode

Decisions If condition is true, then Process step(s) 1 Else Process step(s) 2 End if Is condition True? Process Step(s) 1 Process Step(s) 2 No Yes Flowchart Pseudocode

Average Grade Problem Start Sum=0 Count = 0 Input Grade More grades? Sum = Sum + Grade Count = Count + 1 Average = Sum/Count Stop No Yes Flowchart Pseudocode BEGIN Average Grade sum=0 count = 0 DO WHILE grade > 0 sum = sum + grade count = count +1 END DO average = sum/count END Average Grade