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Project: squares
A project for CSCS1320S14 by Alana Whittier during the Spring Semester 2014.
This project was first begun, on or around, February, 20, 2014 and took approximately 1 week to complete. The program I first submitted is not incorrect, as it does compile and yields the expected output, although it is not necessarily the most elegant or efficient script. In that first program, a series of 'if' and 'else if' statements were used to ensure appropriate execution of the program. After some more consideration, I decided to try writing the program in an entirely different manner, using both the factor and the remainder to achieve the same output as produced in my first program. However, even this endeavor had it's challenges as I am still not sure how to conditionally tell the compiler for ALL values greater than 95, INCLUDING those that end in 5, to only return the error message.
Objectives
The purpose of this project is to become familiarized with using a pointer in order to use the scanf() feature for obtaining input from a user. Also, this project serves to introduce a new user of C programming to conditional statements in order to achieve the desired output. In order to successfully compile and execute the program using a mental math technique, a pointer must be applied appropriately, scanf() must be implemented to call for user input and communicate back to the compiler, and the use of conditional statements (if statements, etc.) must be used.
Prerequisites
In order to successfully accomplish/perform this project, the listed resources/experiences may be consulted/achieved:
Helpful Resources:
- Kernighan, Ritchie The C Programming Language Second Edition, AT&T Bell Laboratories, 1988. Print.
- email consultations and guidance from Matt Haas
Experiences necessary:
- ability to edit code
- ability to use lab46 remotely
- an understanding of the mental math technique to apply to the two digit integers ending in 5 to acquire the square of that number
- a basic understanding of pointers and scanf() to obtain user input
- ability to use conditional statements to achieve desired output
Background
This project implements a mental math technique to compute the square of any two-digit integer ending in 5. A program is written in a manner consistent with the technique described in the project assignment page.
See project assignment page on the provided link.
Project: MENTAL MATH (SQUARES OF 5)
This mental math technique, as well as many others, is part of a collection of what is commonly called Vedic Mathematics, methods to compute quickly, without the use of a calculator, or performing a lengthy multi-step multiplication process by hand.
Scope
The motivation behind this project is to become familiarized with applying a pointer in order to use the Scanf() feature to acquire user input for computing the squares of two-digit integers ending in 5. A program is written in which the Vedic math technique is applied to compute the squares individually and output them for the user.
Attributes
State and justify the attributes you'd like to receive upon successful approval and completion of this project.
- write program to successfully calculate the square of the two-digit integer ending in 5 using the Mental Math Technique
- Obtain user input with a prompt by proper implementation of pointer and use of scanf().
- Output both the user input value and the square of that value.
Procedure
My first attempt at writing the program was using the modulus operator, %, although abandoned that effort quickly as it was not clear what to do with the factor in order to implement the mental math technique. I then decided to implement the computation of the square in what I deemed more simplistic of an approach and then used a series of if, else if statements to output only the values I wanted the user to input and obtain (two-digit integers ending in 5), and finally an else statement in which “Error: Invalid Entry” is displayed for all values greater than 95 and for all values that do not end in 5.
Example 1:
#include <stdio.h> #include <stdlib.h>
int main() {
int i;
int *p;
p=&i;
printf("type up to a two digit integer ending in 5;\n");
scanf("%d", p);
if(i==15){
printf("%.2d: %d\n",i, (1*(1+1))*100 + 5*5);}
else if(i==25){
printf("%.2d: %d\n",i, (2*(2+1))*100 +5*5);}
else if(i==35){
printf("%.2d: %d\n",i, (3*(3+1))*100 +5*5);}
else if(i==45){
printf("%.2d: %d\n",i, (4*(4+1))*100 +5*5);}
else if(i==55){
printf("%.2d: %d\n",i, (5*(5+1))*100 +5*5);}
else if(i==65){
printf("%.2d: %d\n",i, (6*(6+1))*100 +5*5);}
else if(i==75){
printf("%.2d: %d\n",i, (7*(7+1))*100 +5*5);}
else if(i==85){
printf("%.2d: %d\n",i, (8*(8+1))*100 +5*5);}
else if(i=95){
printf("%.2d: %d\n",i, (9*(9+1))*100 +5*5);}
else
printf("Error: Invalid Entry\n");
return(0);
}
After more consideration, I decided to try again writing the program using the modulus operator, which I called R and the factor which I declared a variable. This code is substantially more efficient as it does not require so many lines of code to obtain the squared values. However, I am uncertain how to completely limit the computation and output, since this approach also works for 3 and 4 digit integers ending in five.
See the code below.
#include <stdio.h> #include <stdlib.h>
int main() {
int i;
int factor, R;
int *p;
p=&i;
printf("type up to a two digit integer ending in 5;\n");
scanf("%d", p);
factor = i/10;
R = i % 10;
if(R==5)
printf("%.2d: %d\n",i, (factor*(factor+1))*100 + 5*5 );
if(i>95)
printf("Error: Invalid Entry");
return(0);
}
Code
<code c> /*Squares.c - A program which implements a mental math;
technique for computing the square of any; two digit integer ending in 5, given by user input;
Written by: Alana Whittier for CSCS1320S14 on February 26, 2014;
Compile with: gcc- - squares squares.c; Execute with: ./squares */
#include <stdio.h> #include <stdlib.h>
int main() {
int i;
int *p;
p=&i;
printf("type up to a two digit integer ending in 5;\n");
scanf("%d", p);
if(i==15){
printf("%.2d: %d\n",i, (1*(1+1))*100 + 5*5);}
else if(i==25){
printf("%.2d: %d\n",i, (2*(2+1))*100 +5*5);}
else if(i==35){
printf("%.2d: %d\n",i, (3*(3+1))*100 +5*5);}
else if(i==45){
printf("%.2d: %d\n",i, (4*(4+1))*100 +5*5);}
else if(i==55){
printf("%.2d: %d\n",i, (5*(5+1))*100 +5*5);}
else if(i==65){
printf("%.2d: %d\n",i, (6*(6+1))*100 +5*5);}
else if(i==75){
printf("%.2d: %d\n",i, (7*(7+1))*100 +5*5);}
else if(i==85){
printf("%.2d: %d\n",i, (8*(8+1))*100 +5*5);}
else if(i=95){
printf("%.2d: %d\n",i, (9*(9+1))*100 +5*5);}
else
printf("Error: Invalid Entry\n");
return(0);
}
Execution
lab46:~/src/cscs1320$ nano squares.c lab46:~/src/cscs1320$ gcc -o squares squares.c lab46:~/src/cscs1320$ ./squares type up to a two digit integer ending in 5; 25 25: 625 lab46:~/src/cscs1320$ ./squares type up to a two digit integer ending in 5; 55 55: 3025 lab46:~/src/cscs1320$ ./squares type up to a two digit integer ending in 5; 60 Error: Invalid Entry lab46:~/src/cscs1320$ ./squares type up to a two digit integer ending in 5; 95 95: 9025 lab46:~/src/cscs1320$ ./squares type up to a two digit integer ending in 5; 100 Error: Invalid Entry lab46:~/src/cscs1320$
Reflection
Considering the difficulties I encountered during the process of writing this program, it was as rewarding as it was frustrating. It forced me to delve deeper into more of the computer fundamentals to successfully execute the program. Since I have never taken a digital logic type course and this was my first programming course, binary was a foreign concept to me. Furthermore, converting from decimal to binary or hex was even more foreign. I have learned everything from two's and one's complement, to format specifiers, to manipulating code in order to obtain the negative values in the range for the signed data types. In order to do this, I changed from bitwise AND to bitwise OR, as well as type cast to the unsigned counterpart of the data type. This was a surprise, as I happened upon changing from bitwise AND to OR, only in desperation to achieve what I knew the low values in the range were supposed to be. I kept second guessing MY logic, as well as the computer logic used in completing the assignment.
Observations
The long and long long int (signed and unsigned) appear the same. This is because they are both 64 bit and that is the most the compiler can handle.
printf() and fprintf() basically do the same thing. The difference being that printf can only print on the monitor, has the default stream of STDOUT, while fprintf can print to a user defined stream (or file). In our project, fprintf uses the STDOUT to the screen AS if it were a file.
STDOUT is by default printed to the screen unless user specified.
%s is the format specifier used to print a string of characters, %hhu is the format specifier for half half unsigned char, % hu is the format specifier for unsigned short int.
The difference between %u and %d are that %u denotes an unsigned int type, while %d denotes a signed int type.
Considering the 13 in %13 in the first stanza for unsigned char in the program, this just specifies the number of characters in the string, including spaces to be printed for “TYPE”.
If a sign is left unspecified, it is assumed unsigned by default.
The & and | operators are the bitwise logic operators, which in our case took the hex representation of our data types to help us to obtain the appropriate high/low values within our ranges.
I experienced some difficulty in initial attempts to obtain the low values for the signed data types. I later learned that not only did I need to change the expression for the “low” values to bitwise OR, but I also needed to type cast in the final line of the signed data type stanza.
Based on my program's output, the total bits allocated per the following data types are as follows:
- signed char = 8 bits
- unsigned short int = 16 bits
- unsigned int = 32 bits
- signed int = 32 bits
- signed long long int = 64 bits
However, due to the decrementing and incrementing per data type, only the unsigned char actually stored ANY memory at all and stored a total of 16 bits!
References
In performing this project, the following resources were referenced:
