LECTURE 13

308--208 PHASE 2

1. Learn simple DOS commands
2. Learn to start Turbo C
3. Learn Turbo C editor
4. Understand structure of C program
5. Understand philosophy of C :
             
   • Declare everything           
   • Top-down structure           
   • Reserved keywords           
   • Lots of checking at compile time           
   • TC : lots of checking at execution time           
   • Integrated development environment ( TC )
6. Learn C syntax
7. Do 3 C  assignments
   

Some of the statements in various high­level languages are illustrated in the following table. Each section of code represents the calculation of an employee's salary.

Examples of High­Level Languages

LANGUAGE EXAMPLE STATEMENTS

Pascal:

if hours <= 40.0 then
   salary := hours*payrate
else
   salary := 40.0*payrate +
   (hours ­ 40.0)*payrate*1.5; 

FORTRAN 90:

if (hours <= 40.0) then
   salary = hours*payrte
else
   salary = 40.0*payrte +
   (hours ­ 40.0)*payrte*1.5
endif

Ada:

if hours <= 40.0 then 
   salary := hours*payrate; 
else 
   salary := 40.0*payrate +
   (hours ­ 40.0)*payrate*1.5;

BASIC:

if h > 40.0 then 200
let s = h*p
go to 250
200 let s = 40.0*p + (h ­ 40.0)*p*1.5
250

COBOL:

if hours is less than 40.0 or
_ hours is equal to 40.0,
   compute salary = hours*payrate
else
   compute salary = 40.0*payrate +
   (hours ­ 40.0)*payrate*1.5

PL/I:

if hours <= 40.0 then 
   salary = hours*payrate; 
else 
   salary = 40.0*payrate +
   (hours ­ 40.0)*payrate*1.5;

ADVANTAGES OF C

• Newer, " structured " language
• Designed for better programming
• All identifiers must be declared
• Many control constructs
• Possible to program without GOTO
• Free-format source code
• Reserved keywords
• Heterogeneous data types
• Bit-oriented logical operators
• Almost as ubiquitous as FORTRAN

DISADVANTAGES OF C

• More things to learn
• Errors harder to pinpoint
• No built-in complex data type arithmetic

TURBO C COMPILER :

Hot Key	Menu Equivalent Function
F1	Help Displays a Help screen
F2	File/Save Saves active edit or file
F3	File/Open Opens file
F4	Run/Go to cursor Executes to cursor location
F5	Window/Zoom Zooms the active window
F6	Window/Next Cycles through open windows
F7	Run/Trace into Traces into subroutines
F8	Run/Step over Steps over subroutine calls
F10	Activates the menu bar
ALT-F1	Help/Previous topic Displays previous Help screen
ALT-F3	Window/Close Closes active window
ALT-F5	Window/User screen Displays User screen
ALT-F9	Compile/Compile Compiles active program
ALT-Spacebar	menu Goes to System menu
ALT-C	Compile menu Goes to Compile menu
ALT-D	Debug menu Goes to Debug menu
ALT-E	Edit menu Goes to Edit menu
ALT-F	File menu Goes to File menu
ALT-H	Help menu Goes to Help menu
ALT-O	Options menu Goes to Options menu
ALT-R	Run menu Goes to Run menu
ALT-S	Search menu Goes to Search menu
ALT-W	menu Window Goes to Window menu
ALT-X	menu File/Exit Exits Turbo Pascal to DOS
CTRL-F1	Help/Topic search Gives language-specific help while in editor
CTRL-F2	Run/Program reset Resets running program
CTRL-F7	Debug/Add watch Adds a watch expression
CTRL-F8	Debug/Toggle breakpoint Clears or sets conditional breakpoint
CTRL-F9	Run/Run Executes active program

TURBO C OPERATIONS

Function	Keystroke
Movement Commands	Ctrl S or left arrow
Character left	Ctrl D or right arrow
Character right	Ctrl A or Ctrl left arrow
Word left	Ctrl F or Ctrl right arrow
Word right	Ctrl E or up arrow
Line up	Ctrl X or down arrow
Line down	Ctrl R or PgUp
Page up	Ctrl C or PgDn
Page down	Ctrl Q/S or Home
Beginning of line	Ctrl Q/D or End
End of line	Ctrl Q/E or Ctrl Home
Top of window	Ctrl Q/X or Ctrl End
Bottom of window	Ctrl Q/R or Ctrl PgUp
Beginning of program	Ctrl Q/C or Ctrl PgDn
End of program
Insert and Delete Commands
Delete line	Ctrl Y
Delete block	Ctrl K/Y
Delete to end of line	Ctrl Q/Y
Delete character left of cursor	Ctrl H or Backspace
Delete character under cursor	Ctrl G or Delete
Insert line	Ctrl N
Block Commands
Copy block to edit file	Ctrl K/C
Copy block to Clipboard	Edit/Copy or Ctrl lns
Delete block (not saving to Clipboard)	Edit/Clear or Ctrl Del
Delete block (saving to Clipboard)	Edit/Cut or Shift Del
Hide/display block	Ctrl K/H
Mark block begin	Ctrl K/B
Mark block end	Ctrl K/K
Mark single work	Ctrl K/T
Move block from Clipboard	Edit/Paste or Shift Ins
Move block to edit file	Ctrl-K/V
Read block from disk	Ctrl K/R
Write block to disk	Ctrl K/W
Miscellaneous
Find	Ctrl Q/F or Search/Find
Find and replace	Ctrl Q/A or Search/Replace
Invoke main menu	F10
Language help	Ctrl F1
Open file	F3 or File/Open
Save file	Ctrl K/S or F2 or File/Save

FORTRAN PROGRAM

PROGRAM SINE

! Prints values of y=sin x for x=0,10,...90 degrees.

implicit none

real :: scalef, degree, radian, y
integer :: i

scalef = 3.141593/180.0
print *,'DEGREES SINE FUNCTION'
do i = 0,9
   degree = i*10.0
   radian = scalef*degree
   y = sin(radian)
   print 5,degree,y
5  format (' ',F7.1,F12.4)
end do
stop
END PROGRAM SINE

EQUIVALENT PROGRAM IN C

/* Prints values of y=sinx for x=0,10,...90 degrees. */

#include <stdio.h>
#include <math.h>

main()
{
   float scalef, degree, radian, y;
   int i;
   scalef = 3.141593/180.0;
   printf ("DEGREES SINE FUNCTION\n");
   for (i=0; i<=9; i=i+1)
   {
      degree = i*10.0;
      radian = scalef*degree;
      y = sin(radian);
      printf ("%f7.1%f12.4\n",degree,y);
   }
}

FORTRAN FORM VS. C FORM

FORTRAN 77 ---> RIGID FORMAT (Improved with FORTRAN 90)

• Actual statements go in columns 7--72 only
• Labels go in columns 1--5 only
• One statement per line
• Long line must use continuation in column 6
• Comments on separate lines
• Keywords can be used as variables (IF=5)
• Spaces allowed in keywords and variables

C ---> FREE FORMAT

• Statements can go anywhere on a line
• Use punctuation to separate statements
• Multiple statements per line ( Don't abuse this ! )
• Some parts of statements separated by '' white space '' ( spaces, tabs, carriage-returns )
• Long lines usually can be split in nice places ( use \ if needed )
• Comments can be on same lines as statements
• Reserved keywords
• No spaces in keywords and variables

DATA TYPES IN C

int same as INTEGER ; float same as REAL

Most expressions are the same as FORTRAN :
(Where op is an arithmetic operator + - * / %)

• int op int => int
• int op float=> float
• float op int = float
• float op float=> float
• Precedences the same

BUT THERE ARE DIFFERENCES :

• " a % b " in C like " MOD ( A,B ) " in FORTRAN
• " pow( a,b ) " in C like " A**B " in FORTRAN

CHAR TYPES IN C

1) char in C like CHARACTER*1 in FORTRAN

• Char constants are single characters within single quotes : 'A'
• Special characters represented with backslash combinations :

Form	Meaning
\0	null character
\b	backspace
\f	form feed (top of page)
\n	new line
\r	carriage return
\t	tab
\v	vertical tab
\'	single quote ( ' )
\"	double quote ( " )
\\	backslash ( \ )
\%	percent sign ( % )

• May be used like integers ( c - '@' turns A--Z into 1--26 )

2) char(n) in C like CHARACTER (LEN=n) in FORTRAN

• Strings terminated with \0 (null char)
• Thus, a string can have a ''length'' -- even be empty!
• String constants are enclosed within double quotes : "A"
• Use ' [i] ' to get at ith character : init = name[1]
• Illegal ( but not detected ! ) if i bigger than declared length

A Complete C Program

Example #1 :

#include <stdio.h>

main( )
{
   printf("Hello, world\n");
}

#include <stdio.h>

main()
{
   printf("The value of PI is about 3.14159 \n");
}

#include <stdio.h>
#define PI 3.14159

main()
{
   printf("The value of PI is %f \n", PI);
}

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