1 midterm 1 review. 2 midterm 1 on friday february 27 closed book, closed notes no computer can be...
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3 C Numeric Data TypesTRANSCRIPT
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Midterm 1 Review
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Midterm 1 on Friday February 27 Closed book, closed notes No computer can be used 50 minutes 4 or 5 questions
write full programs write partial programs find output of a program
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C Numeric Data Types
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C Character Data Type: char
In memory, everything is stored as binary value, which can be interpreted as char or integer. Examples of ASCII Codes
char result =‘Y’;
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Precedence of Arithmetic Operators
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Standard Input and Output Output: printf Input: scanf
Remember the program computing the distance between two points!
/* Declare and initialize variables. */ double x1=1, y1=5, x2=4, y2=7, side_1, side_2, distance; How can we compute distance for different points? It would be better to get new points from user, right?
For this we will use scanf To use these functions, we need to use
#include <stdio.h>
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Standard Output printf Function
prints information to the screen requires two arguments
control string Contains text, conversion specifiers or both
Identifier to be printed Example
double angle = 45.5;printf(“Angle = %.2f degrees \n”, angle);
Output:Angle = 45.50 degrees
Control String
Identifier
Conversion Specifier
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Math Functionsfabs(x) Absolute value of x.
sqrt(x) Square root of x, where x>=0.
pow(x,y) Exponentiation, xy. Errors occur if x=0 and y<=0, or if x<0 and y is not an integer.
ceil(x) Rounds x to the nearest integer toward (infinity). Example, ceil(2.01) is equal to 3.
floor(x) Rounds x to the nearest integer toward - (negative infinity). Example, floor(2.01) is equal to 2.
exp(x) Computes the value of ex.
log(x) Returns ln x, the natural logarithm of x to the base e. Errors occur if x<=0.
log10(x) Returns log10x, logarithm of x to the base 10. Errors occur if x<=0.
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Relational Operators == equality (x == 3) != non equality (y != 0) < less than (x<y) > greater than (y>10) <= less than equal to (x<=0) >= greater than equal to (x>=y)
!!! a==b vs. a=b !!!
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Logical Operators ! not !(x==0) && and (x>=0) && (x<=10) || or (x>0) || (x<0)A B A && B A || B !A !BFalse False False False True TrueFalse True False True True FalseTrue False False True False TrueTrue True True True False False
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Precedence for Arithmetic, Relational, and Logical Operators
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If statement if(Boolean expression)
statement; //single statement if(Boolean expression) { //more than one statement
statement1;.statement n;
}
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if - else statement if(Boolean expression)
statement;else
statement; if(Boolean expression)
{statement block
}else{
statement block}
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Loop (repetition) statements while statement do while statement for statement
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while statement while(expression)
statement; while(expression)
{ statement;statement;
.}
x=1;while (x<5) x = x + 1;
x = 1;while (x<5){ x = x+1; printf(“X=“%d”,x);}
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do while do
statement;while(expression);
do{statement1;statement2;.} while(expression);
note - the expression is tested after the statement(s) are executed, so statements are executed at least once.
x=1;do x = x + 1;while (x<5);
x = 1;do{ x = x+1; printf(“X=“%d”,x);} while (x<5);
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for statement for(initialization; test; increment/decrement)
statement;
for(initialization; test; increment/decrement){statement;statement;.}
for (x=1; x<5; x++) printf(“x=%d\n”,x);
for (x=1; x<5; x++){ printf(“X=“%d\n”,x); printf(“X^2 = %d\n”,x*x);}
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for statement
initalizetest
increment/decrement
true
statement(s)statement(s)
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Data FilesEach data file must have a file pointer
file pointer must be defined FILE *sensor1; FILE *balloon;
file pointer must be associated with a specific file using the fopen function
sensor1 = fopen(“sensor1.dat”, “r”); balloon = fopen(“balloon.dat”, “w”);
Read information from file
Write information
to a file
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I/O Statements Input file - use fscanf instead of scanf
fscanf(sensor1, “%1f %lf”, &t, &motion);
Output file - use fprint instead of printf fprintf(balloon, “%f %f %f\n”, time,
height, velocity);
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Reading Data Files counter controlled loop
First line in file contains count for loop
end of file controlled loop When file is created EOF is inserted while loop feof(fileptr) > 0 when EOF reached
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End of file controlled loop#include <stdio.h>
int main(){ FILE *scorefile; int score;
scorefile = fopen("scores.txt","r");
while (feof(scorefile) <= 0) { fscanf(scorefile,"%d",&score); printf("%d\n",score); }
fclose(scorefile); return(0);}
File
567893248563
Available on webpage as chapter3e11.c
Available on webpage as scores.txt
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Functions Defined to
return a single value to the calling function
perform a task change the value of the function
arguments (call by reference)
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Function Format
return_type function_name (parameter_declarations)
{declarations;statements;
}
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Example - factorial function
int fact(int n){ int factres = 1; while(n>1) {
factres = factres*n;n--;
} return(factres);}
n!=n*(n-1)*…*1, 0! = 1 by definition
Return Type Function name
Parameter DeclarationsDeclarations
Statements
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Example - factorial function
int main(void){ int t= 5,s; s=fact(t)
return 0;}
5t
s
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Example - factorial function
int main(void){ int t= 5,s; s=fact(t)
return 0;}
int fact(int n){ int factres = 1;
return(factres);}
5t
s
n
factres
5
1
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Example - factorial function
int main(void){ int t= 5,s; s=fact(t)
return 0;}
int fact(int n){ int factres = 1;
return(factres);}
5t
s
n
factres
5
120 120
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Example - factorial function
int main(void){ int t= 5,s; s=fact(t)
return 0;}
5t
s120
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Arrays
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Definition and Initialization An array is defined using a declaration statement. data type array_name[size];
allocates memory for size elements subscript of first element is 0 subscript of last element is size-1 size must be a constant
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Exampleint list[5];
allocates memory for 5 integer variables subscript of first element is 0 subscript of last element is 4 C does not perform any bounds checking on
arrayslist[0]
list[1]list[2]list[3]
list[4]
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Initializing Arrays Arrays can be initialized at the time they
are declared. Examples:
double taxrate[3] ={0.15, 0.25, 0.3};char list[5] = {‘h’,’e’,’l’,’l’,’o’};double vector[100] = {0.0}; /*assigns zero to all 100
elements*/int s[] = {5,0,-5}; /*the size of a s is 3 */
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Assigning values to an arrayfor loops are often used to assign values to an array
Example:
int list[5], i;for(i=0; i<5; i++){
list[i] = i;}
list[0]
list[1]list[2]list[3]
list[4]
01234
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Exercise int data[100] Store random numbers [0,99) in data
for (i=0; i<100; i++) data[i] = rand() % 100;
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Function Arguments Individual elements of an array can be
passed as regular arguments. void donothing(int a, int b){…}int main(void){ /* Declare variables and functions */int array[5] = {1,2,3,4,5};
donothing(array[2], array[4]);..}
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Passing Arrays to Functions Arrays are always pass by reference
Modifications to the array are reflected to main program
The array name is the address of the first element The maximum size of the array must be specified at
the time the array is declared. The actual number of array elements that are used
will vary, so the actual size of the array is usually passed as another argument to the function
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Exercise
int maximum(int fdata[], int n){ int i, fmax; fmax = fdata[0]; for (i=0; i<n; i++) if (fdata[i] > fmax) fmax = fdata[i]; return(fmax);}
int data[100]Write a function to find maximum value in the array data
int main(){ int data[100],i, max;
for (i=0; i<100; i++) data[i] = rand() % 100; max = maximum(data,100); printf("Max = %d\n",max); return(0);}
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Exercisevoid print(int pdata[], int n){ int i; for (i=0; i<n; i++) printf("data[%d]=%d\n",i,pdata[i]); return;}void modify(int fdata[], int n){ int i; for (i=0; i<n; i++) fdata[i] = 1; return;}
What is the output of the following program?int main(){ int data[10];
for (i=0; i<10; i++) data[i] = rand() % 100; print(data,10); modify(data,10); print(data,10);
return(0);}