A complete C-program

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A complete C-program
Display Fig. 2.1 and comment on different things
such as Preprocessor directives Header
files Identifiers Directives Constants Variables S
tandard Identifiers (Predefined
functions)1 Punctuations Special symbols Reserved
words
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Figure 1.11 Miles-to-Kilometers Conversion
Program / Converts distance in miles to
kilometers. / include ltstdio.hgt
/ printf, scanf definitions / define
KMS_PER_MILE 1.609 / conversion constant
/ int main(void) double miles,
/ input - distance in miles. /
kms / output - distance in kilometers
/ / Get the distance in miles. /
printf("Enter the distance in milesgt ")
scanf("lf", miles) / Convert the
distance to kilometers. / kms
KMS_PER_MILE miles / Display the
distance in kilometers. / printf("That
equals f kilometers.\n", kms) return
(0) Sample Run Enter the distance in milesgt
10.00 That equals 16.090000 kilometers.
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User defined identifiers

• Consists of letters, digits, underscore
• Cannot begin with a digit
• A C-reserved word cannot be used
• A standard identifier should not be redefined
• Dont use more than 31 charcters
• Examples
• Letter, letter_1, myfunc_1, square_meter

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Variables and data types

• Variables are names of different memory cells
  that can hold values of different types
• The name of a variable is an identifier
• A variable should be declared as a certain data
  type
• Examples
• int n, no_of_students
• float score, sum, mean_value

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Example cont.

• double miles / miles from here to there/
• char letter, digit
• Variables of type int can store integers in
  INT_MIN, INT_MAX and similar for float and
  double but they can store a real number with an
  integral and fractional part
• A char can hold one single charcter

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How to write int,double,float,charconstants
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Assignment statements

• A variable can get its value via an assignment
  statement
• Ex.
• define PI 3.141596
• int n
• double radius, perimeter
• n10
• radiusnn(n-1)/6
• perimeter2PIradius
• Comment on evaluation order etc.(more on this in
  Ch. 3)

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Syntax of printf()

• printf(format string, print list)
• printf(format string)
• Ex.
• printf(\nRadius is f and perimeter, radius)
• printf( is 10.2f\n, perimeter)
• This is a prompting message or prompt
• printf(Type radius in cm )
• scanf(lf, radius)
• Read more about formating in section 2.5

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Syntax of scanf()

• scanf(format string, input list)
• Ex.
• int age
• double weight / in kilogram /
• printf(Type your weight and age in one line )
• scanf(lfd, weight, age)
• Note
• age denotes a pointer to (address to) the
  variable age

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Program Style

• Use spaces in the code
• Use comments in a clever way (say what the
  intention is)
• See Program Comment on page 49 in text book
• Read about Case Study on page 50

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Input/output redirection

• Instead of giving the input interactivly from the
  keyboard data can be taken from a file (text
  file)
• Ex. assume the executable file is called myprog
• Run by typing
• ./myprog ltmyin_1 gtmyout_1
• Now scanf() reads from myin_1 and printf() writes
  to myout_1
• myin_1 should be a text file in the same
  directory as myprog
• Note! No prompting in the program in this case

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Program controlled Input/output from/to text files

• See page 59-61 for an overview but you can leave
  it for now
• (uses file pointers)

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Run-time errors

• When reading to char-varibles there is a risk
  that inputed characters hanging in the input
  buffer will cause subsequent reading to fail
• See Fig. 2.13 page 65

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Figure 2.13 Function main for Disc
Characteristics with Revised Beginning
int main(void) char part_id1, part_id2,
/ input - 3-character part id /
part_id3 double radius, / input -
radius of disc in cm / area,
/ output - area of disc in cm2 /
circum / output - circumference of disc (cm)
/ / Get the disc radius /
printf("Enter radius (in centimeters)gt ")
scanf("lf", radius) fflush(stdin)/otherwise
part_id1 fails/ / Get the part
identifier / printf("Enter a 3-character
part i.d.gt ") scanf("ccc", part_id1,
part_id2, part_id3) / Calculate the
area / area PI radius radius
/ Calculate the circumference / circum 2
PI radius / Display the part i.d.,
area and circumference / printf("For part
ccc, ", part_id1, part_id2, part_id3)
printf("the disc area is f cm2.\n", area)
printf("The circumference is f cm.\n", circum)
return (0)