PHY 107 – Programming For Science

The Week’s Goal

Announcements  Weekly assignment #2 available on to D2L

Program Outline  Once upon a time…  … some stuff happens…  … and they all lived happily ever after

Program Outline  Once upon a time…  All programs must begin somewhere  Defines what is worked upon during rest of program  For non-trivial programs, requires receiving input  When starting program, first steps always same: 1. What is the input? 2. What will the input look like? 3. How will the data be entered?

Reading From The Keyboard  Easiest to get input from the keyboard  Reading from files possible; discussed later in term  C lacks standard, so writing GUI program harder  C defines scanf to get user’s input  As easy to use as delivering food to Granny’s house  When scanf hit, program waits until it has input  User must press enter for line to be able to be read  Editing not seen by program; only receives final line

Even Better Magic  Must tell scanf types it will be reading read Variable TypeSpecifier int%i, %d long int%li, %ld unsigned int%u unsigned long%lu float%f, %e, %E, %g, %G double%lf, %le, %lE, %lg, %lG long double%Lf, %Le, %LE, %Lg, %LG char%c

Programming Using scanf

Warning #1 will not  Incorrect scanf specifier will not trigger an error  Specifier, not variable, determines data read

Warning #2 will not  Incorrect scanf specifier will not trigger an error  Specifier, not variable, determines data read  Illegal assignments allowed, but result is ugly

Warning #3 will not  Incorrect scanf specifier will not trigger an error  Specifier, not variable, determines data read  Illegal assignments allowed, but result is ugly  YOUR RESPONSIBILITY to check in C/C++

scanf Example

Program Outline  Once upon a time…  Get the input using scanf from the keyboard  … some stuff happens…  … and they all lived happily ever after

Some Stuff Happens  This really depends on specific project details  Focus of most of term, we will skip this today

Program Outline  … and they all lived happily ever after  All good processing comes to end & report results  Shows program worked and provides feedback  Results takes many forms, focus on printing today  When starting program, second steps ask: 1. What must be output? 2. How can output be presented best? 3. Will it be pretty?

Using printf to Print  Already seen how to print text using printf printf(“Hello World\n”);  Prints out whatever is placed between quotes  Use escape sequences for fancier text output \n  newline (move to start of next line) \t  tab (go to next column that is multiple of 8) \\  \ (backslash character) \”  “ (quotation mark)

Can Print Out Multiple Items  printf can also print out value of variables int bob = 2; double j = 4.5; char var = ‘a’; printf(“Hello ”); printf(“%d\n”, bob); printf(“%lf\n”, j); printf(“%c\n”, var); printf(“%lf is not %d”, j, bob); printf(“%d equals bob\n”, bob); printf(“%c%d%lf”, var, bob, j);

But Can It Be Used?  printf built to provide basics needed to work  Prints out as many digits as needed  No extra spaces or tabs used  Scientific notation cannot be used  Often want to format results  Significant digits can matter  Tables make reading faster

Formatting Output #include #include int main() { int k = 4, bigK = 100; double stuff = ; printf(“%d\n”, k); printf(“%3d%d\n”, k, k); printf(“%-4d%2d\n”, k, bigK); printf(“%05d\n”, bigK); printf(“%lf\n”, stuff); printf(“%06lf\n”, stuff); printf(“%.2lf\n”, stuff); printf(“%10.2lf\n”, stuff); }

Your Turn  Get in groups & work on following activity

For Next Lecture