CECS 121 REACH Final Test Review

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CECS 121 REACH Final Test Review
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Test Review Topics

• Old Material
• escape sequences
• operator precedence
• printf()
• scanf()
• if()
• switch case
• ,
• while, do-while, , --
• functions

New Material 1-D arrays string functions fopen() f
close() fscanf() fprintf()
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Escape Sequences

• Definition Escape sequences are specially
  sequenced characters used to format output
• \
• Ex printf( \ This is quoted text \ )
• \
• Ex printf( \n A single quote looks like \
  \n)
• \ \ Comment Block

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Directives

• include ltstdio.hgt
• Using a directive to include a header file
• Stdio.h standard input output header file

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Memory

• A computers long-term memory is called
  nonvolatile memory and is generally associated
  with mass storage devices, such as hard drives.
• A computers short term memory is called volatile
  memory. It loses is data when power is removed
  from the computer, such as RAM

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Data Types
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
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Variable Types
TYPE SIZE VALUES
bool 1 byte true (1) or false (0)
char 1 byte a toz , A to Z, 0 to 9, space, tab, and so on
int 4 bytes -2,147,483,648 to 2,147,483,647
short 2 bytes -32,768 to 32,767
long 4 bytes -2,147,483,648 to 2,147,483,647
float 4 bytes - (1.2 x 10-38 to 3.4 x 1038)
double 8 bytes - (2.3 x 10-308 to -1.7 x 10308)
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Arithmetic and Order of Precedence
Operator Description
Multiplication
/ Division
Modulus (remainder)
Addition
- Subtraction
Order of Precedence Description
( ) Parentheses are evaluated first, from innermost to outermost
, /, Evaluated second, from Left to Right
, - Evaluated last, from Left to Right
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printf() scanf()

• Can you explain what the code is doing?

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Can you predict the printout?

• int main()
• printf (c c \n", 'a', 65)
• printf ("d ld\n", 1977, 650000L)
• printf (" 10d \n", 1977)
• printf ("010d \n", 1977)
• printf ("floats 4.2f \n", 3.1416)
• printf ("s \n", "A string")
• printf(f \n, 55.55)
• return 0

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Printouts

• printf (c c \n", 'a', 65) aA
• printf ("d ld\n", 1977, 650000L) 1977650000
• printf (" 10d \n", 1977)
  1977
• printf ("010d \n", 1977) 0000001977
• printf ("floats 4.2f \n", 3.1416)
  3.14
• printf ("s \n", "A string") A string
• printf(f \n, 55.55) 55.550000

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Review Printing with Precision
Example Printout
printf(.1f,3.123456) 3.1
printf(\n.2f,3.123456) 3.12
printf(\n.3f,3.123456) 3.123
printf(\n.4f,3.123456) 3.1235
printf(\n.5f,3.123456) 3.12346
printf(\n.6f,3.123456) 3.123456
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scanf

• Syntax
• scanf(conversion specifier, variable)

Conversion Specifies Description
d Receives integer value
f Receives floating-point number
c Receives character
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Can you predict the printout when the user enters
2 and 4?

• include ltstdio.hgt
• main()
• int iOperand1 0
• int iOperand2 0
• printf(\n Enter first operand )
• scanf(d, iOperand1)
• printf(\n Enter second operand )
• scanf(d, iOperand2)
• printf(The result is d \n, 24/(iOperand1
  iOperand2)6/3)

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Boolean Operators

• Do you know the answers to these?
• A. !( 1 0 )
• B. !( 1 1 0 )
• C. !( ( 1 0 ) 0 )

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Boolean Operators Quiz Answers

• A. !( 1 0 ) ANSWER 0
• B. !( 1 1 0 ) ANSWER 0 (AND is
  evaluated before OR)
• C. !( ( 1 0 ) 0 ) ANSWER 1 (Parenthesis
  are useful)

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If Statements
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Quiz

• Can you write code that will ask a user to enter
  a number 1 , 2 , or 3 and print out the
  following

User Input Printout
1 1 is the loneliest number
2 2 is better than 1
3 3s a crowd
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Answer

• int a
• int main()
• printf (Enter one of the following d, d, or
  d\n, 1, 2, 3)
• scanf(d, a)
• if(a1 a2 a 3)
• if(a1)
• printf(\n d is the loneliest number \n, 1)
  
• if(a2)
• printf(\nd is better than d \n,2,1)
• if(a3)
• printf(\nd \ s a crowd \n,3)
• else
• printf(Sorry, you entered an invalid value\n)

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Switch-Case Statments
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Example Switch-Case Statement
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Loops

• while ( condition ) Code to execute while the
  condition is true
• Quiz Can you write a program that prints x
• while x increments from 0 to 10?

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Answer While Quiz
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• do while ( condition )
• What is the main difference between Do while
  and while?

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Answers

• while ( condition ) Code to execute while the
  condition is true
• do while ( condition )
• Do while() executes code at least once!

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Questions

• How do you generate a new line?
• What will happen if a user tries to enter a
  decimal into scanf(d, number)
• What does each of the following do?
• , - , , / , , , gt , lt

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FOR Loops

• Use when the number of iterations is already
  known
• Syntax

for ( variable initialization condition
variable increment/decrement) Code to execute
while the condition is true
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Can you predict the printout?
include ltstdio.hgt int main() int x for
( x 0 x lt 10 x ) printf(
"d\n", x ) getchar()
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Practice FOR Loops

• Write a program using a FOR Loop to display all
  of the multiples of 5 from 0 to 100.

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Answer
include ltstdio.hgt int main() int x for
( x 0 x lt 20 x ) printf(
"d\n", x5 ) getchar()
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Incrementing/Decrementing

• x x-- Postfix
• x --x Prefix

main() int x 0 int y 0 printf(\n The
value of y is d \n, y) printf(\n The value
of x is d \n, x)
Answer 0 1
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BREAK and CONTINUE

• Use to manipulate flow in loops
• What does a Break statement do when executed
  within a loop?
• What does a Continue statement do when executed
  within a loop?

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Break and Continue Example
include ltstdio.hgt main() int x for ( x
10 x gt5 x-- ) if (x7)
break printf( \n d \n , x )
include ltstdio.hgt main() int x for ( x
10 x gt5 x-- ) if (x7)
continue printf( \n d \n , x )

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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
  parameters, how many parameters, and the order of
  parameters
• Function definitions implement the function
  prototype
• Where are function prototypes located in the
  program?
• Where do you find function definitions?

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Function Prototypes

• Where are function prototypes located in the
  program?
• Answer before the main() Function!
• Function Definitions are self contained outside
  of the main() function

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Calling Functions
include ltstdio.hgt int mult ( int, int) int
main() int x int
y printf( "Please input two numbers to be
multiplied " ) scanf( "d", x ) scanf(
"d", y ) printf( "The product of your two
numbers is d\n", mult( x, y ) ) getchar()
int mult (int a, int b) return a b
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Whats Wrong with This Code?
include ltstdio.hgt printNumber() main() int
x printNumber(x) printNumber() printf(\
n The number is d \n, x)
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Answer
include ltstdio.hgt void printNumber( int x)
main() int x printNumber(x) void
printNumber(int y) printf(\n The number is d
\n, y)
Note its not absolutely necessary to write
VOID, but its a good practice.
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Can You Pick Out the Local and Global Variables?
include ltstdio.hgt void printNumbers() int
iNumber main() int x for(x0,
xlt10,x) printf(\n Enter a
number) scanf(d, iNumber) printNumbers
() void printNumbers() printf(\n Your
number is d \n, iNumber)
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Variable Scope

• Variable scope defines the life time of a
  variable
• Local Scope defined within functions and loses
  scope after function is finished. Can reuse in
  other functions (ex. p.123)
• Global Scope defined outside of functions and
  can be accessed by multiple functions

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Challenge Question

• Can you write code that asks a user to input 4
  integers, adds the numbers together in one
  function, multiplies them in another, and finally
  prints out the difference between the sum and
  product? The user should have to do this 5 times.

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ANSWER (one option)
include ltstdio.hgt int addNumbers(int, int,
int, int) int multNumbers(int, int, int, int)
main() int a, b, c, d, counter0
while(counterlt6) printf(\n Please
enter 4 integers separated by spaces\n) scanf(
d d d d, a, b, c, d) printf(\n d
\n, addNumbers(a,b,c,d)-multNumbers(a,b,c,d)) c
ount int addNumbers(int f, int g,
int h, int y) return fghy int
multNumbers(int f, int g, int h, int y) return
fghy
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How to Declare a One-Dimensional Array

• Can you declare a one-dimensional array made up
  of 10 integers?
• Answer int iArray10
• How to declare an Array
• int iArray10
• float fAverages30
• double dResults3
• short sSalaries 9
• char cName19 //18 characters and 1 null
  character

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How to Initialize a 1-D Array

• Why do we initialize? Because memory spaces may
  not be cleared from previous values when arrays
  are created
• Can initialize an array directly
• Example int iArray50,1,2,3,4
• Can initialize an array with a loop such as FOR()

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Example of Initializing an Array Using a For()
Loop
include ltstdio.hgt main() int x int
iArray5 for( x0 x lt 5 x)
iArrayx 0
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Printing Arrays

• Can you add code to print out the values of the
  program below?

include ltstdio.hgt main() int x int
iArray5 for( x0 x lt 5 x)
iArrayx 0
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Answer
include ltstdio.hgt main() int x int
iArray5 for( x0 x lt 5 x)
iArrayx 0 for(x0 xlt5 x)
printf(\n The value of iArray index d is d
\n, x, iArrayx)
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Accessing the elements in an array

• How do you search through an array?

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include ltstdio.hgt main() int x int
iValue int iFound -1 int iArray5 for(
x0 x lt 5 x) iArrayx
(xx) printf(\n Enter value to search
for) scanf(d, iValue) for(x0 xlt5
x) if( iArrayx iValue)
iFound x break
) if(iFound gt-1) printf(\n I found
your search value in element d \n,
iFound) else printf(\n Sorry, your
search value was not found \n)
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String functions
Function Description
strlen(str) Returns numeric string length up to, but not including null character
tolower(str) and toupper(str) Converts a single character to upper or lower case
strcpy(str1, str2) Copies the contents of str2 string into str1 string.
strcat(str1, str2) Appends str2 string onto the end of str1 string.
strcmp(str1,str2) Compares two strings for equality. A zero value indicates that both strings are equal.A value greater than zero indicates that the first character that does not match has a greater value in str1 than instr2 And a value less than zero indicates the opposite.
strstr(str1, str2) Searches the first string for the first occurrence of the second string. A pointer to the first occurrence in str1 of any of the entire sequence of characters specified in str2, or a null pointer if the sequence is not present in str1.
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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 bytes i.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
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Simple Data Structures
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Passing Structures to Functions
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Sizeof()
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Malloc()
Please enter how long your name is 21 Please
enter your name Nawaf Hello Nawaf
Please enter how long your name is -7 Failed
allocation memory
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free()
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Calloc and Realloc()

• int n
• int n1
• n( int ) calloc(5, sizeof(int)) //
  Reserves a block of memory for 5 integers
• //Decide you need to reallocate more memory later
  in the program
• n1 (int ) realloc(n, 10 sizeof(int))//allocat
  e 10 integers instead of 5
• if (n1!NULL)
• nn1
• else printf("Out of memory!")
• realloc() returns null if unable to complete or a
  pointer to the newly reallocated memory.

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New Material-

• Do you know the syntax for each of these, used to
  read and write to data files?
• Pointers think of it as the memory address of
  the file
• fopen()
• fclose()
• fscanf()
• fprintf()

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fopen(file name, Mode)

• fopen() returns a FILE pointer back to the pRead
  variable

include ltcstdiogt Main() FILE pRead pRead
fopen(file1.dat, r) if(pRead NULL)
printf(\nFile cannot be opened\n) else
printf(\nFile opened for reading\n) fclose(p
Read)
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Common Text File Modes
Mode Meaning Already Exists Does Not Exist
r Open a file for reading read from start error
w Create a file for writing destroy contents create new
a Append to a file write to end create new
r Open a file for read/write read from start error
w Create a file for read/write destroy contents create new
a Open a file for read/write write to end create new
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fclose(file pointer)

• Pretty basic, yet important.

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fscanf(FILE pointer, data type, variable in
which to store the value)

• Reads a single field from a data file
• s will read a series of characters until a
  white space is found
• can do fscanf(pRead, ss, name, hobby)

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• include ltstdio.hgt
• Main()
• FILE pRead
• char name10
• pRead fopen(names.dat, r)
• if( pRead NULL )
• printf( \nFile cannot be opened\n)
• else
• printf(\nContents of names.dat\n)
• fscanf( pRead, s, name )
• while( !feof(pRead) )
• printf( s\n, name )
• fscanf( pRead, s, name )
• fclose(pRead)

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Quiz
Kelly 11/12/86 6 Louisville Allen 04/05/77 49 At
lanta Chelsea 03/30/90 12 Charleston
Can you write a program that prints out the
contents of this information.dat file?
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• include ltstdio.hgt
• main()
• FILE pRead
• char name10
• char birthdate9
• float number
• char hometown20
• pRead fopen(information.dat, r)
• if( pRead NULL )
• printf( \nFile cannot be opened\n)
• else
• fscanf( pRead, ssfs, name0,
  birthdate, number, hometown )
• while( !feof(pRead) )
• printf( s \t s \t f \t
  s\n, name, birthdate, number, hometown )

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fprintf(FILE pointer, list of data types,list
of values or variables)

• The fprintf() function sends information (the
  arguments) according to the specified format to
  the file indicated by stream. fprintf() works
  just like printf() as far as the format goes.

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• include ltstdio.hgt
• main()
• FILE pWrite
• char fName20
• char lName 20
• float gpa
• pWrite fopen(students.dat,w)
• if( pWrite NULL )
• printf(\nFile not opened\n)
• else
• printf(\nEnter first name, last name, and GPA
  separated
• printf(Enter data separated by spaces)

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Quiz

• Can you write a program that asks the user for
  their
• Name
• Phone Number
• Bank account balance
• And then prints this information to a data file
  called accounts.dat ?

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Questions?
Good Luck in your final Exam from REACH
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References

• TEXTBOOK RESOURCE C Programming for the
  Absolute Beginner 2nd Edition by Michael Vine
• www.cprogramming.com

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Quiz
Kelly 11/12/86 6 Louisville Allen 04/05/77 49 At
lanta Chelsea 03/30/90 12 Charleston
How many fields are there? How many records are
there? How many bytes are there in the first
record? How many bits are there in Kelly?