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Unit 3.2Understand Loop Control Structures
   At the end of this presentation, students will be    able to:    ◦ Understand looping control structures    ◦ Describe...
   Looping statements are used to :    ◦ execute a set of instructions repeatedly, as long as the      specific condition...
   Syntax:    for(initialization;condition; incrementation/decrementation)      {         //loop statements       }   Ex...
   initialization    ◦ refer to initial value of loop counter    ◦ carried out just once at the beginning of loop   cond...
   The program LoopDemo.cpp illustrates the working    of a for loop.
#include<iostream>using namespace std;int main(){                                      12345678910    int num;    for (num...
   There are a few patterns that you often need:     ◦ To go from zero to some maximum – 1:         for (i = 0; i < max; ...
   Is a looping statement that enables you to repeat a set    of instructions based on a condition.   If the condition i...
   Syntax:    <initialise variable>     while(condition)     {       //loop statements     <Increment/decrement variable>...
   Example:    while ((amount >0 && amount <=balance)    {        balance = balance – amount;        cout << “Please take...
   Program While1.cpp illustrates the working of a    while loop.
#include<iostream>using namespace std;int main(){                      1 3 5 7 9 11  int x=1;  while(x<=11){  cout<<x<<" "...
   The do-while loop is similar to the while loop.   The difference only in the location where the    condition is check...
   Example    do {       cout << “Enter a value";       cin >> i;       if ( i<=0)       {            cout << “This is ne...
   Program DoWhileDemo.cpp illustrates the    working of a do-while loop.
#include<iostream>using namespace std;int main()                  1 3 5 7 9 11{    int x=1;        do        {            ...
while                   do-while           is      no                     i = i+1        i > 10?             yes          ...
   Allow program controls to transfer from one part to    another part of program unconditionally   4 types of jump stat...
   break    ◦ The break statement causes termination of the loop      and transfers the control outside the loop.    ◦ Pr...
#include<iostream>using namespace std;int main(){                                         Entering into the loop   int i; ...
   continue    ◦ can only be used inside a loop.    ◦ The continue statement will transfer the control to the      beginn...
#include<iostream>using namespace std;int main(){         for(int i=1;i<=10;i++)                  13579         {         ...
   return    ◦ terminate execution of current function AND return      value contained in the expression to the function ...
   goto    ◦ useful when you want to exit from a deeply nested      loop.    ◦ control flow statement that causes the CPU...
#include <iostream>#include <cmath>using namespace std;void main(){   tryAgain: // this is a statement label   double numb...
In this presentation, you learnt the following: Looping   statements are used to execute a set of instructions repeatedly...
 The continue statement will transfer the control to  the beginning of the loop. The return statement will terminate exe...
if (( x > 3) && (y < 7))1.    Consider the following                                       cout << "E";      code fragment...
   3 and 7      4 and 7                   ACFG    ACFH                 4 and 8   3 and 6       BCFG    ACFG
2.   What is the output?#include<iostream>using namespace std;int main(){      int sum=0, item=0;      while (item<5) {   ...
item<5   0      1     2   3    4item++   1      2     3   4    5if(item==2)      continue;sum+=item;   1      4     8   13
3.   Write a program that can produce an output as     below by using the for, while, and do-while loop                   ...
   for loop//solution 1#include<iostream>using namespace std;int main(){  for(int k=4; k>=1;k--)  cout<<k*2<<endl;return ...
//solution 2#include<iostream>using namespace std;int main(){  for(int k=8; k>=1;k--)  {  cout<<k<<endl;  k--;  }return 0;}
 while loop//solution 1#include<iostream>using namespace std;int main(){    int k=4;    while(k>=1)    {    cout<<k*2<<en...
//solution 2#include<iostream>using namespace std;int main(){    int k=8;    while(k>=1)    {    cout<<k<<endl;    k--;   ...
   do-while loop//solution 1#include<iostream>using namespace std;int main(){    int k=4;    do{          cout<<k*2<<endl...
//solution 2#include<iostream>using namespace std;int main(){    int k=8;    do{          cout<<k<<endl;          k--;    ...
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FP 201 - Unit 3 Part 2

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FP 201 - Unit 3 Part 2

  1. 1. Unit 3.2Understand Loop Control Structures
  2. 2.  At the end of this presentation, students will be able to: ◦ Understand looping control structures ◦ Describe the structure and working of for, while and do-while loops ◦ Explain the need for break, continue, return and goto statements
  3. 3.  Looping statements are used to : ◦ execute a set of instructions repeatedly, as long as the specific condition is satisfied. The loop in C++ comes in 3 forms: ◦ for ◦ while ◦ do-while
  4. 4.  Syntax: for(initialization;condition; incrementation/decrementation) { //loop statements } Example: for (i=0; i<5; i++) { cout << “n” << i ; }
  5. 5.  initialization ◦ refer to initial value of loop counter ◦ carried out just once at the beginning of loop condition(expression) ◦ determined whether loop should continue ◦ if expression is false the loop will be terminate Incrementation/decrementation ◦ The initial value of the loop control variable is either incremented or decremented each time the loop gets executed.
  6. 6.  The program LoopDemo.cpp illustrates the working of a for loop.
  7. 7. #include<iostream>using namespace std;int main(){ 12345678910 int num; for (num = 1; num <= 10; num++) { cout<<num; } return 0;}
  8. 8.  There are a few patterns that you often need: ◦ To go from zero to some maximum – 1: for (i = 0; i < max; ++i) ◦ Or, in the opposite direction: for (i = max - 1; i >= 0; --i) ◦ Or To go from 1 to some maximum: for (i = 1; i <= max; ++i) ◦ Or, in the opposite direction: for (i = max; i > 0; --i) You might sometimes need a combination of elements from more than one of these patterns, such as for (i = 0; i <= max; i++), but if you write something unusual like this, make sure that it really is what you want.
  9. 9.  Is a looping statement that enables you to repeat a set of instructions based on a condition. If the condition is TRUE executes loop statement(s) in the while block and executing its block until the condition is FALSE.
  10. 10.  Syntax: <initialise variable> while(condition) { //loop statements <Increment/decrement variable>; } Expression is evaluated first ◦ If expression = TRUE then statement is executed ◦ If expression = FALSE then statement is bypassed
  11. 11.  Example: while ((amount >0 && amount <=balance) { balance = balance – amount; cout << “Please take your money” << amount; cout << “This is your balance” << balance; }
  12. 12.  Program While1.cpp illustrates the working of a while loop.
  13. 13. #include<iostream>using namespace std;int main(){ 1 3 5 7 9 11 int x=1; while(x<=11){ cout<<x<<" "; x=x+2; } return 0;}
  14. 14.  The do-while loop is similar to the while loop. The difference only in the location where the condition is checked. In do-while, condition is checked at the end of loop.Syntax<initialise variable> do { //loop statements <Increment/decrement variable>; } while(condition);
  15. 15.  Example do { cout << “Enter a value"; cin >> i; if ( i<=0) { cout << “This is negative number"; } } while (i>0);
  16. 16.  Program DoWhileDemo.cpp illustrates the working of a do-while loop.
  17. 17. #include<iostream>using namespace std;int main() 1 3 5 7 9 11{ int x=1; do { cout<<x<<" "; x=x+2; }while(x<=11); return 0;}
  18. 18. while do-while is no i = i+1 i > 10? yes print i print i yes is i > 10? i = i+1 no
  19. 19.  Allow program controls to transfer from one part to another part of program unconditionally 4 types of jump statement: ◦ break ◦ continue ◦ return ◦ goto
  20. 20.  break ◦ The break statement causes termination of the loop and transfers the control outside the loop. ◦ Program BreakDemo.cpp illustrates the use of break statement.
  21. 21. #include<iostream>using namespace std;int main(){ Entering into the loop int i; 123456789 cout<<"Entering into the loopn"; Exiting out of the loop for(i=1;i<20;i++) { if(i==10) break; // exit from for loop cout<<i<<" "; } cout<<"nExiting out of the loopn";return 0;}
  22. 22.  continue ◦ can only be used inside a loop. ◦ The continue statement will transfer the control to the beginning of the loop. ◦ Program ContinueDemo.java illustrates the use of continue statement.
  23. 23. #include<iostream>using namespace std;int main(){ for(int i=1;i<=10;i++) 13579 { if(i%2==0) continue; cout<<i<<" "; } return 0;} The continue statement is executed when i%2==0. The continue statement ends the current iteration so that the rest of the statement in the loop body is not executed; therefore, i is printed when i%2!=0.
  24. 24.  return ◦ terminate execution of current function AND return value contained in the expression to the function that invoked it. Example: float CalcSum() { float sum; sum = 15 + 20; return sum; }
  25. 25.  goto ◦ useful when you want to exit from a deeply nested loop. ◦ control flow statement that causes the CPU to jump to another spot in the code. Syntax goto identifier ; Example: goto tryAgain;
  26. 26. #include <iostream>#include <cmath>using namespace std;void main(){ tryAgain: // this is a statement label double number; cout << "Enter a non-negative number: "; cin >> number; if (number < 0.0) goto tryAgain; // this is the goto statement cout << "The sqrt of " << number << " is " << sqrt(number) << endl;}
  27. 27. In this presentation, you learnt the following: Looping statements are used to execute a set of instructions repeatedly, as long as the specific condition is satisfied. In C++, the looping control structures include while, do-while and for. The break statement will transfer the control to the statement outside the loop.
  28. 28.  The continue statement will transfer the control to the beginning of the loop. The return statement will terminate execution of current function and return the value. The goto may be necessary for exiting a loop from within a deeply nested loop.
  29. 29. if (( x > 3) && (y < 7))1. Consider the following cout << "E"; code fragment: else cout << "F"; cin >> x >> y; if (( x > 3) || (y < 7)) if ((x >= 3) && (y <= cout << "G"; 7)) else cout << "A"; cout << "H"; else cout << "B"; if ((x >= 3) || (y <= 7)) ◦ What is the output cout << "C"; produced if the user else cout << "D"; enters:  3 and 7  3 and 6  4 and 7  4 and 8
  30. 30.  3 and 7  4 and 7 ACFG ACFH  4 and 8 3 and 6 BCFG ACFG
  31. 31. 2. What is the output?#include<iostream>using namespace std;int main(){ int sum=0, item=0; while (item<5) { item++; if(item==2) continue; sum+=item; } cout<<"The sum is"<<sum;}
  32. 32. item<5 0 1 2 3 4item++ 1 2 3 4 5if(item==2) continue;sum+=item; 1 4 8 13
  33. 33. 3. Write a program that can produce an output as below by using the for, while, and do-while loop 8 6 4 2
  34. 34.  for loop//solution 1#include<iostream>using namespace std;int main(){ for(int k=4; k>=1;k--) cout<<k*2<<endl;return 0;}
  35. 35. //solution 2#include<iostream>using namespace std;int main(){ for(int k=8; k>=1;k--) { cout<<k<<endl; k--; }return 0;}
  36. 36.  while loop//solution 1#include<iostream>using namespace std;int main(){ int k=4; while(k>=1) { cout<<k*2<<endl; k--; }return 0;}
  37. 37. //solution 2#include<iostream>using namespace std;int main(){ int k=8; while(k>=1) { cout<<k<<endl; k--; k--; }return 0;}
  38. 38.  do-while loop//solution 1#include<iostream>using namespace std;int main(){ int k=4; do{ cout<<k*2<<endl; k--; }while(k>=1);return 0;}
  39. 39. //solution 2#include<iostream>using namespace std;int main(){ int k=8; do{ cout<<k<<endl; k--; k--; }while(k>=1);return 0;}

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