CECS 130 Mid-term Test Review - PowerPoint Presentation

CECS 130 Mid-term Test Review Provided by REACH – Resources for Academic AchievementPresenter: REACH Nikhil Paonikar CECS 130 Mid-term Exam Review Summer, 2019

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Data Type Description Declaration Example Integer Whole numbers, positive or negative int x = ; -3 , 0, 3 , 29 Floating-point number All numbers, positive or negative, decimals and fractions float x = ; -0.35543 , 0.00, 554433.33281 Character Representations of integer values known as character codes char x = ‘ ’; m, M, @ To declare a constant (read only) value: const int x = 20; const float PI = 3.14; Variable Types

TYPE SIZE VALUES bool1 byte true (1) or false (0)char 1 byte‘a’ to‘z’ , ‘A’ to ‘Z’, ‘0’ to ‘9’, space, tab, etc.int 4 bytes -2,147,483,648 to 2,147,483,647short 2 bytes -32,768 to 32,767long 4 bytes -2,147,483,648 to 2,147,483,647 float 4 bytes + - (1.2 x 10^-38 to 3.4 x 10^38) double 8 bytes+- (2.3 x 10^-308 to -1.7 x 10^308)Variable Types

scanf( ) ; printf( ) int x = 0; printf(“ What number should I print out? \n ”); scanf(“%d”, &x); //variables require an “&” sign before them for scanf()! printf(“\n You chose: %d \n”, x); //but not for printf()!!

Conversion Specifiers Character - %c Integer - %d Float (decimal)- %f String - %sprintf Format Tags:Format: %[flags][width][.precision][length]specifier Example: %[.precision]specifier Output: 7 | float fboat = 12.123432; 8 | printf( “%.2f, %.3f, %.5f”, fboat, fboat, fboat ); 12.12, 12.123, 12.12343

Arithmetic, Logic and Order of Precedence Operators Description ( ), !( ) Parentheses: evaluated from innermost to outermost *, /, % Multiplication: evaluated from left to right + , - Addition: evaluated from left to right <, <=, >, >= Inequalities: evaluated from left to right ==, != Equalities: evaluated from left to right &&, || Logical expressions: &&’s first, then ||’s. *This is a highly abbreviated list. See https://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence for the full order of precedence.

1 | #include <stdio.h>2 | 3 | int main()4 | {5 | int iNum_1= 0; 6 | int iNum_2= 0; 7 | 8 | printf( “Please enter first number: ” ); 9 | scanf( “%d”, &iNum_1 ); // (user enters 2) 10| printf( “\nEnter second number: ” ); 11| scanf( “%d”, &iNum_2 ); // (user enters 4) 12| printf( “\n\nThe result is %d. \n”, 24 / (iNum_1 * iNum_2) + 6 / 3);13| 14| return 0; 15| } Predict the printout: User enters ‘2’ and ‘4’:

1 | #include <stdio.h>2 | 3 | int main()4 | {5 | int iNum_1= 0; 6 | int iNum_2= 0; 7 | 8 | printf( “Please enter first number: ” ); 9 | scanf( “%d”, &iNum_1 ); 10| printf( “\nEnter second number: ” ); 11| scanf( “%d”, &iNum_2 ); 12| printf( “\n\nThe result is %d. \n”, 24 / (iNum_1 * iNum_2) + 6 / 3);13| 14| return 0; 15| } Output:Please enter first number: 2Enter second number: 4The result is 5. Predict the printout: User enters ‘2’ and ‘4’:

1 | #include <stdio.h>2 | 3 | int main()4 | {5 | int x = 9; 6 | int y = 4; 7 | int result1, result2; 8 | 9 | result1 = x/y; 10| result2 = x%y; 11| 12| printf ( “\n\nThe result is %d.%d”, result1, 25 * result2);13| } Can you predict the printout?

1 | #include <stdio.h>2 | 3 | int main()4 | {5 | int x = 4; 6 | int y = 9; 7 | int result1, result2; 8 | 9 | result1 = y/x; 10| result2 = y%x; 11| 12| printf ( “\n\nThe result is %d.%d \n”, result1, 25 * result2);13| } Can you predict the printout? Output:The result is 2.25

Conditions and Operators Operator Description == Equal to != Not Equal > Greater Than < Less Than >= Greater Than or Equal to Order of Precedence Description && AND condition || OR condition

Comparisons > greater than 5 > 4 is TRUE < less than 4 < 5 is TRUE >= greater than or equal 4 >= 4 is TRUE <= less than or equal 3 <= 4 is TRUE == equal to 5 == 5 is TRUE!= not equal to 5 != 4 is TRUE

Boolean Operators Do you know the answer to these? A. !( 1 | | 0 ) B. !( 1 | | 1>0 && 0 ) C. !(( 1 | | 1>0 ) && 0)

Boolean Operators B. A. C. Answers: !( 1||0 ) =!( 1 ) = 0 !(1|| 1<0 &&0) =!(1|| 0 &&0) =!(1||0) =!(1) = 0 !((1|| 1<0 )&&0) =!(( 1|| 0 )&&0) =!( 1 &&0 ) =!( 0) = 1

Example Using if-statements, write a program that will ask a user to enter a number 1, 2, or 3, and print out the following: User Input Printout 1 Smitty Werbenjagermanjensen was Number 1. 2 Fool me 2 times, can’t put the blame on you. 3 Gimme 3 steps.

1 | #include <stdio.h>2 | int main() { 4 | printf( “Enter one of the following: %d, %d, or %d\n”,1,2,3 );5 | scanf( “%d”, &a ); 6 | if(a==1||a==2||a==3) { 7 | if(a==1)8 | printf(“\nSmitty Werbenjagermanjensen was Number %d.\n ”, 1); 9 | if(a==2) 10| printf(“\nFool me %d times, can’t put the blame on you.\n ”, 2);11| if(a==3) 12| printf(“ \dGimme %d steps.\n ”, 3); 10| }11| else 12| printf(“\nSorry, you entered an invalid value\n” );16| return 0; Example:

1 | switch ( <var> )2 | { 3 | case <this-value>:4 | code to execute if <var> == this-value; 5 | break; 6 | case <that-value>:7 | code to execute if <var> == that-value; 8 | break; 9 | ... 10| default:11| code executed if <var> does not equal any of the values; 12| break; 13| } Switch-Case Statement

The while( ) loop while ( condition ) { Code to execute while the condition is true } 1 | #include <stdio.h> 2 | int main() 3 | { 4 | int x = 0; 5 | 6 | while ( x < 10 )7 | { 8 | printf( “%d”, x ); 9 | x++;10| printf(“\nFool me %d times, can’t put the blame on you.\n”, 2);11| }12| getchar();13| }

The for( ) loop Often used when the # of iterations is already known. Contains 3 separate expressions: Variable initialization Conditional expression Increment/Decrement 1 | #include <stdio.h> 2 |3 | int main()4 | { 5 | int x = 0; 6 | for( x=10; x>=0; x-- ) {7 | printf( “%d\n”, x );8 | }9 |}

Break/Continue Statements break; Used to exit a loop. Once this statement is executed the program will execute the statement immediately following the end of the loop. continue; Used to manipulate program flow in a loop. When executed, any remaining statements in the loop will be skipped and the next iteration of the loop will begin.

Function Prototypes & Definitions Function Prototype Syntax return-type function_name ( arg_type arg1, ..., arg_type argN ) Function Prototypes tell you the data type returned by the function, the data type of the function’s parameters, how many parameters it takes, and the order of parameters.Function definitions implement the function prototypeWhere are function prototypes located in the program? Where do you find function definitions?

Function Prototypes & Definitions Where are function prototypes located in the program? Answer: before the main( ) { } function. Where do you find function definitions? Answer: function definitions are self-contained outside of the main( ) { } function, usually written below it.

Function Example #include <stdio.h> int mult (int,int); // function prototype int main() { int x; int y; int z; printf( “\n x = "); scanf( "%d", &x ); printf( “\n y = ”); scanf( "%d", &y ); printf( “\n z = ”); scanf( "%d", &z ); printf( “\n x*y = %d\n", mult ( x, y ) ); printf( “\n z^2 = %d\n", mult( z, z ) ); } int mult (int a, int b) { //function definition return a * b;}

Function Example #include <stdio.h> int mult (int,int); // function prototype int main() { int x; int y; int z; printf( “ x = " ); scanf( "%d", &x ); printf( “\n y = ”); scanf( "%d", &y ); printf( “\n z = ”); scanf( "%d", &z ); printf( “\n\n x*y = %d\n", mult( x, y ) ); printf( “\n z^2 = %d\n", mult( z, z ) ); } int mult (int a, int b) //function definition{ return a * b;} Output: x = 2 y = 3 z = 4 x*y = 6z^2 = 16

Declaring a 1-D Array How do you declare a one-dimensional array made up of 10 integers? Answer: int iArray[10] Other array declarations: int iArray[10]; float fAverages[30]; double dResults[3]; short sSalaries [9]; char cName[19]; // 18 characters and 1 null character

Declaring a 1-D Array Why do we initialize variables? Because memory spaces may not be cleared from previous values when arrays are created. Can initialize an array directly. E.g.: int iArray[5]={0,1,2,3,4}; Can also initialize an array with a loop such as FOR( ) #include <stdio.h> main() { int x; int iArray[5]; for( x=0; x < 5 ; x++) { iArray[x] = x; } }

Example: searching an array #include <stdio.h> int main() { int x, iValue; int iFound = -1; int iArray[5]; // initialize the array for( x=0; x < 5 ; x++) { iArray[x] = ( x + x ); // array will = { 0, 2, 4, 6, 8 } } printf(“\n Enter value to search for:”); scanf(“%d”, &iValue); // search for number for(x=0 ; x<5; x++) { if( iArray[x] == iValue) { iFound = x; break; } } if(iFound > -1) printf(“\n I found your search value in element %d \n”, iFound); else printf(“\n Sorry, your search value was not found \n”); return 0;}

Pointers Pointer variables, simply called pointers, are designed to hold memory addresses as their values. Normally, a variable contains a specific value, e.g., an integer, a floating-point value, or a character. However, a pointer contains the memory address of another variable .

Pointer Syntax dataType *pointer_name = &variable_name; (You can also initialize it “…= NULL;” or “… = 0;”) It’s important to initialize pointers to prevent fatal runtime errors or accidentally modifying important data.

Pointers int val = 5; //variable declaration int *val_ptr = &val; //pointer declaration 0x3F *val_ptr 0x83 5 val 0x3F name: Value Value name: location: location:

Pointers When an ampersand (&) is prefixed to a variable name, it refers to the memory address of this variable. 0x3F *val_ptr &val_ptr = 0x83 5 val &val = 0x3F name: Value Value name: location: location:

Ampersand example #include <stdio.h> int main() { char someChar = 'x'; printf(“%p\n", &someChar); return 0; } Output: ?????

Passing variables with pointers void exchange(int*, int*); main() { int a = 5; int b = 3; exchange(&a,&b); [(3)print a and b] } //pass by reference void exchange(int *x, int *y) { [(1)print *x and *y] int temp = *i; int *x = *y; int *y = temp; [(2)print *x and *y]}Output:*x = 5, *y = 3*x = 3, *y = 5a = 3, b = 5void exchange(int, int); main() { int a = 5; int b = 3; exchange(a,b); [(3)print a and b] }//pass by value void exchange(int x, int y) { [(1)print x and y] int temp = x; int x = y; int y = temp; [(2)print x and y] } Output: (1) x = 5, y = 3 (2) x = 3, y = 5 (3) a = 5, b = 3 Output: (1) x = 5, y = 3 (2) x = 3, y = 5 (3) a = 3, b = 5

Pointers to Arrays An array variable without a bracket and a subscript represents the starting address of the array. An array variable is essentially a pointer. Suppose you declare an array of integer values as follows: int list[6] = {11, 12, 13, 14, 15, 16}; *(list + 1) is different from *list + 1. The dereference operator (*) has precedence over +. So, *list + 1 adds 1 to the value of the first element in the array, while *(list + 1) dereferences the element at address list[1] in the array.

Pointers to Arrays main() { int list[3] = {10, 3, 5}; int k = 0; k = *list + 1; printf(“k = %d”, k); } Output: k = 11 main() { int list[3] = {10, 3, 5}; int k = 0; k = *(list + 1); printf(“k = %d”, k);} Output: k = 3

Strings Function Description strlen() Returns numeric string length up to, but not including null character tolower() and toupper() Converts a single character to upper or lower case strcpy() Copies the contents of one string into another string strcat() Appends one string onto the end of another strcmp() Compares two strings for equality strstr() Searches the first string for the first occurrence of the second string

Strings #include <stdio.h> #include <string.h> int main() { char *str1 = “REACH”; char str2[] = “Tutoring”; printf(“\nThe length of string 1 is %d \n”, strlen(str1)); printf(“\nThe length of string 2 is %d \n”,strlen(str2)); return 0; } Output: The length of string 1 is 5 The length of string 2 is 8

Strings #include <stdio.h> #include <string.h> void convertL(char *); int main() { char name1[] = “Barbara Bush”; convertL(name1); return 0; } void convertL(char *str) { int x; for ( x = 0; x <=strlen(str) ; x++) str[x] = tolower(str[x]); printf(“\nThe name in lowercase is %s\n”, str);}Output: The name in lowercase is barbara bush

Data File Hierarchy Entity Description Bit Binary digit, 0 or 1 Smallest value in a data file Byte Eight bits Stores a single character Field Grouping of bytesi.e a word, social security number Record Grouping of fields a single row of information, student name, age, ID, GPA File Grouping of records separate fields in a record using spaces, tabs, or commas

Data Structures Arrays require that all elements be of the same data type. It is often necessary to group information of different data types. An example is a list of materials for a product. The list typically includes a name for each item, a part number, dimensions, weight, and cost. C and C++ support data structures that can store combinations of character, integer, floating point and enumerated type data. They are called - structs.

Struct Syntax struct oneCar //elements in a list of cars { int year; char make[10]; char model[10]; char tag[8]; }fleet; //for short we’ll call it a fleet fleet rentals[5]; // five cars that we rent out to clients rentals[0].year = 2008; rentals[0].make = “Honda”; rentals[0].model = “Element”; rentals[0].tag = “AS2395”; […] rentals[4].year = 2015; rentals[4].make = “Tesla” rentals[4].model = “Model S”;rentals[4].tag = “2FST4U”;fleet vans[3]; //company vansvans[0].year = 2012; vans[0].make = “Ford”;vans[0].model = “EconoVan”; Vans[0].tag = “MV1NUP”;

Dynamic memory allocation These functions are defined in the <stdlib.h> header file. void *calloc(int num, int size) Allocates an array of num elements each of whose size in bytes will be size.void free(void *address) Releases a block of memory block specified by address. void *malloc(int num) Allocates an array of num bytes and leave them uninitialised. void *realloc(void *address, int newsize) Re-allocates memory extending it up to newsize.

Implementing malloc()

Implementing calloc()

Resizing and releasing memory using realloc() and free()

Some types of problems you will likely encounter:True/False questions Fill-in-the-blanks questionsFinding errors in programsCommon mistakes on this test:Not appending lines of code with a semicolon (“;”)Forgetting to use semicolons when writing a FOR loop Forgetting to add an ampersand (“&”) to your variable parameter in SCANF functions (and mistakenly using the ampersand when using PRINTF) Mixing up * and & in general.Off-by-one errors when accessing an array, especially when using a FOR loop. On the test…

Avoid extensive studyConduct a brief reviewDo something relaxingGet plenty of sleep Avoid stress-inducing situationsMaintain a positive attitude Test Success: The Night Before

Get off to a good start.Arrive on time or early.Compose yourself.Do a final revision of your notes. Maintain a confident attitude. Test Success: Day of the Test comic by KC Green (http://gunshowcomic.com/648)

Hope for the best, prepare for the worst. Cheers and good luck! This presentation was provided by REACH – Resources for Academic Achievement (If you have not signed in, please do so before you leave!)

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