PHY 107 – Programming For Science

Final Exam  Wed., Dec. 16 th from 2:45PM – 4:45PM in OM110  For exam, plan on using full 2 hours  If major problem, come talk to me ASAP  Exam covers material from entire semester  Open-book & open-note so bring what you’ve got  Your cell phone, parents, & computers are not allowed  Cannot collaborate with a neighbor on the exam  Problems will be in a similar style to midterms

Positional Notation  To convert d n... d 3 d 2 d 1 d 0 into decimal: From base-b d 0 * b 0 d 1 * b 1 d 2 * b 2 d 3 * b 3 … + d n * b n

Converting Decimal To Base-b  General way to convert from decimal to base-b: While decimal number ≠ 0 Divide decimal number by b Move remainder to left end of answer Replace decimal number with quotient

Input Using scanf

Input Using fscanf and FILE*

Output using printf  Already seen how to print text using printf printf(“Hello World\n”); printf(“%d years old”, age);  Prints out whatever is placed between quotes  Print variables’ values with specifier and adding after  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)

Output using fprintf & FILE*  File output easy to write text using fprintf FILE * fOut = fopen(fileName, “w”); fprintf(fOut,“Hello World\n”); fprintf(fOut,“%d years old”, age);  Prints out whatever is placed between quotes  Print variables’ values with specifier and adding after  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)

Even Better Magic  Identifiers for scanf and printf calls TypeSpecifier char%c int%i, %d long int%li, %ld float%f, %e, %E, %g, %G double%lf, %le, %lE, %lg, %lG cString%s

Priority of Operations  Equations can become very complex  * 6 * = …?  Very  Very strict order of operations used by computer  ( ) Solve from inner- to outermost  + (positive) & - (negative) Solve from right to left  * & % & / (division) Solve from left to right  + (addition) & - (subtraction) Solve from left to right use lots of parentheses  My suggestion: use lots of parentheses

Compound Assignment Operators  Short simple operators that allow us to be lazy  Save some typing for several common actions  Lowest priority operation; expression evaluated first OperatorEquivalent C++ Expression a += 2;a = a + 2;a = a + 2; b -= d;b = b – d;b = b – d; c *= ;c = c * ( ); d /= 0.3 * e;d = d / (0.3 * e);

Mathematical Functions  Add #include at top of file  All these functions return a value  Will NOT change argument’s value sin( x ), cos( x ), tan( x ), asin( x ), atan( x ), log10( x ), sqrt( x ), log( x ), exp( x ), pow( x, y ), floor( x ), ceil( x )

Relational Operators  < ( less than)  > ( greater than)  <= ( less than of equal to)  >= ( greater than of equal to)  != ( inequality ≠)  == ( equality – if two things have same value) assignment (=)  NOT the same as assignment (=)

if (…) statement  First evaluates expression in parenthesis  Add opening brace ( { ) after closing parenthesis  Can now write all statements to execute  Add closing brace ( } ) to show where if ends  If expression false, execution restarts at that point  If expression is true, executes code in block  Skips over block, when expression is false

if – else if – else Usage  Must begin with if statement at the start  This is required; what would we be saying else to?  Only  Only required part of this entire process  Can then have zero or more else if s  Tests can be anything; do not have to be related  Until one is true, will be examined one-by-one  Execute 1 st clause where true expression is found  Only at the very end can have else clause  If nothing else matches then else is executed

Executing switch Statement 1. Evaluates expression 2. Finds matching case or default (if it exists)  If no default, may not have match - skips switch 3. Execution starts at 1 st matching label  Execution will continue until break; found  Will continue into next case if break; is not hit 4. Restarts running after switch once break hit  May reach end of switch without a break  Continues running code after switch

while Loop while (expression) { statement;... }  Evaluates expression to find its value  If true, executes entire loop body  Re-check after each pass through loop, only  Continue with loop while expression checks true

for Loop

Function Definition

return Statement

Declaring Arrays

Mistakes with Arrays

String Theory!

Important String Functions  strlen(s)  Counts characters in s before null character  strcpy(s,t)  Copies characters in t into s.  strcat(s,t)  Appends t to end of s.  strcmp(s,t)  Returns negative int if s t, and 0 if s==t  strupr(s)  Converts all characters in s to uppercase  strlwr(s)  Converts all characters in s to lowercase  strncpy(s,t,n)  Copied first n characters from t to s

Opening a File 3

Reading & Writing Binary Data  Computers find binary data easier, faster, & better  Stores data as 0 s & 1 s it uses internally to record info  Except for char s, nearly impossible for humans to read  Specific functions needed to read/write binary  Program can have data written using fwrite()  fread() reads from file into your program

Reading & Writing Binary Data  Computers find binary data easier, faster, & better  Stores data as 0 s & 1 s it uses internally to record info  Except for char s, nearly impossible for humans to read  Specific functions needed to read/write binary  Program can have data written using fwrite()  fread() reads from file into your program All other functions read & write text

& and * Operators variable  & operator gets the address of a variable  Used only with variables  Used only with variables, including array elements  Types must match, no automatic promotion possible  Use * for value at location targeted by pointer  * could also be multiply so only used with pointers  Exception is when variable declared  To declare variable is a pointer, need the * double x, *y; y = &x; x = *y + 2;

Pointers versus Arrays  Both types of variables store an address  Can be assigned to one another if types match  To access value, can either use * or [ index ]  *p same as p[0] - they are "synonyms" in C  Arithmetic works similarly - *(p+5) same as p[5]  Do not get carried away exploiting this idea  Unlike arrays, memory not reserved for pointer  Arrays not used to alias other variables (usually)

Arrays vs. Pointers Arrays = Yams Sweet PotatoesPointers = Sweet Potatoes Yams  Makes space at declaration  Variable value is address  Use [] to access entries  Can also access using *  Can be assigned a pointer  Needs target to be useful  Variable value is address  Use * to access target  Can also access using []  Can be assigned array Often use pointers & arrays interchangeably

malloc() and free()  malloc(…) creates array on heap ptr = malloc( arrayLength * sizeof( entry type ));  ptr should be pointer to entry type  Can use literal, expression, or variable for arrayLength  Array can be returned since heap outlives frame  free(varName) to stop using memory  Argument must be address of 0 th entry in array  SHOULD  SHOULD NOT USE ARRAY after it has been freed  Within program can call free() at any time

Using struct s variables  Can assign struct variables to one another  Variables must be of identical struct types  Copies value of all fields but still remain independent  Locations will be same, since pointers & arrays aliased  In all other situation, must use fields  Cannot add, multiply, compare struct variables  For any legal use, individual fields always available  Arrays of struct s can also be declared  Within the array, each entry is struct variable

“Subtle” Hint

For Final  You can use on this final:  Your textbook & notes  At the same time, you may NOT use:  Computer, calculator, cell phone, or similar  Friends, Romans, countrymen or their ears

How to Prepare for Midterm DODON'T  Redo activities, labs, weekly…  Make cheat sheets for the test  Review how parts of C/C++work  Assume notes replace studying  Ever, ever invade Russia in winter  Assume you'll pass cause you're cute

How to Prepare for Midterm DODON'T  Redo activities, labs, weekly…  Make cheat sheets for the test  Review how parts of C/C++work  Assume notes replace studying  Ever, ever invade Russia in winter  Assume you'll pass cause you're cute

Final Exams Dec. 15, 12:30 – 1:30 in OM115  Mastery Exam for PHY107L: Dec. 15, 12:30 – 1:30 in OM115 Dec. 16, 2:45 – 4:45 in OM110  Final Exam for PHY107: Dec. 16, 2:45 – 4:45 in OM110