Problem-solving

Review

GNG 1106

Reminder

Deliverable 1 of the project is due Nov 29, 2020 at 11:59 pm.

Problem Solving Method - An Example

Problem

A train leaves city A travelling towards city B at some given speed (km/h). At the same time a train leaves city B going to city A at some given speed (km/h). Write a program that will compute the distance from city A where the trains will pass each other.

Multiple Choice

What is the first step of problem solving?

• Identification

• I/O Information Gathering

• Test Cases and Design

• Implementation

• Testing and Verification

Step 1: Identification

• In this case the problem is rather simple and unambiguously defined so step 1 is simply a re-statement of the problem described:

• –A train leaves city A travelling towards city B at some given speed (km/h). At the same time a train leaves city B going to city A at some given speed (km/h). Write a program that will compute the distance from city A where the trains will pass each other.

Multiple Choice

In which step of problem-solving do we start coding/programming?

• 1

• 2

• 3

• 4

• 5

Step 4: Implementation

It is actually step 4 where the coding should start after identifying the problem, analyzing its parameters, and designing the solution.

Multiple Select

In plotting using PLPLOT library, which of the following is the correct order of the functions that needs to be used for plotting?

• plinit, plstring, plssub, plline, plend

• plstar, plenv, plend, pllab, plline

• plinit, plenv, plcol0, plpoin, plend

• plstar, plenv, plcol0, plline, plenv, plpoin, plend

Plplot library

• plinit to initialize the plot.

• plenv to define the range and scale of the graph, axes, etc. (pllab can be used to set the labels on the graph).

• One or more calls (can draw more than one curve on the set of axes) to plline or plpoin to draw lines or points.

• plend, to close the plot.

Fill in the Blanks

In File I/O, if we would like to open the file “test.dat” for reading and writing, without changing the content and having the initial position at the end, we use the line:


filePtr = fopen(“test.dat”, "

" );

Flow chart – Open file modes

Open Ended

Why is the null check important in this following code? And what is the exact type of errors does it handle?

FILE *filePtr;

filePtr = fopen(“test.dat”, “r”);

if(filePtr == NULL)

__printf(“Error encountered opening file.\n”);

NULL Check in File I/O

If there was an error opening the file then fopen returns the NULL address which helps in avoiding Run-time errors.

 E.g.: FILE *filePtr;

  filePtr = fopen(“test.dat”, “r”);

  if(filePtr == NULL)

       printf(“Error encountered opening file.\n”);

Poll

Did you guys have fun reviewing the material?

• Yes

• No