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Table of Contents
Part 1
Entries
Entry 1: January 31, 2012
Today we played more with pointers. We wrote another program which delved into the realm of double pointers. I think I understand pointers but I may be over-simpplifing them. Esssentialy, they direct the computer to another location. When called to give the information contained in them they return the value of what they are pointing to.
Entry 2: Febrauary 2, 2012
Todday we wrote a game in class. We used some elements of things that we used in previous classes as well as looked into loops. We also looked at the rand function which is supposed to resemble a random number generator but doesn't do it very well. We did go through and fix the problem which did make it more random. We also added a loop into the code which looped the game until the user decides to quit. I understand this program and what it is doing, which is a good sign. I haven't gotten lost in the class yet which is always a hopeful start.
Entry 3: February 7, 2012
Today we looked at arrays. My previous experince with arrays is limited to the theoretical realm. I understood that arrays needed to be sized before you start to fill them but I never was quite sure how to actually create them in a program. Today's class helped. I am still not 100% comfortable with creating them on my own but I do see how it can be done.
Entry 4: February 25, 2012
Today Project 1 was due and it was rather more challenging than previously thought. I understand the logic of how to do the program and I understand what needs to be done on the project, however, I am struggling with the actual implementation of the code. When I sit to write the code I essentially draw a blank and have no idea where to begin. I believe that if I sit down more with a pseudocode and play more with syntax and read source material on how to code in C I can overcome this dilemma. Otherwise, this will be a very difficut semester.
Keywords
cprog Keywords
Standard I/O
(STDIO, STDOUT, STDERR)
Definition
The main libraries in which C programs run
Demonstration
#include <stdio.h>
Logic Operators
AND, OR, NOT, XOR
Definition
Specifies the parameters of the loop and determines if the loop should execute
Demonstration
while((x!='\0')&&(x!='\n'))
This is an AND operator in a program
Typecasting
Definition
taking one form of variable and making it fit into another form of variable
Demonstration
Demonstration of the chosen keyword.
If you wish to aid your definition with a code sample, you can do so by using a wiki code block, an example follows:
#include <stdio.h> #include <stdlib.h> int main() { int *p1, *p2, p3, **p4; p1=(int*)malloc(sizeof(int)*1); *p1=26; printf("*p1 is %u\n", *p1); p2=p1; p4=&p1; printf("**p4 is %u\n",**p4); printf("*p2 is %u\n",*p2); *p2=61; printf("*p1 is %u\n", *p1); printf("**p4 is %u\n", **p4); printf("*p2 is %u\n", *p2); return(0); }
This allocated memory in the size of an int
Pointers
Definition
Sets the memory address for something
Demonstration
#include <stdio.h> int main() { int a=0; int *b; b=&a; *b=12; printf("a contains %u\n", a); printf("a's address is 0x%x\n", &a); printf("b contains %u\n", *b); printf("b points to 0x%x\n", b); printf("b's address is 0x%x\n", &b); return(0); }
b is a pointer to a
Arrays
Definition
Holds many different elements of the same data type at one address
Demonstration
#include <stdio.h> #include <stdlib.h> int main() { char *word, len=0, x, pos=0; word=(char *)malloc(sizeof(char)*24); fprintf(stdout, "Please enter a word: "); fscanf(stdin, "%s", word); printf("Debug A\n"); x=*(word+pos); printf("Debug A1\n"); while((x!='\0')&&(x!='\n')) { printf("in the while, x is %hhd\n",x); len++; pos++; x=*(word+pos); } printf("Debug B\n"); for(pos=0; pos<len; pos++) { fprintf(stdout, "%c", *(word+pos)-32);
File Access
read, write append
Definition
Creating a file and reading it into a program or writing the output of a program to a file
Demonstration
#include <stdio.h> #include <stdlib.h> int main() { FILE *in, *out; char value=0; in=fopen("file.txt", "r"); out=fopen("out.txt", "w"); if(in==NULL) { printf("ERROR!\n"); exit(1); n, *out; char value=0; in=fopen("file.txt", "r"); out=fopen("out.txt", "w"); if(in==NULL) if(in==NULL) if(in==NULL) } fscanf(in, "%hhd", &value); while(value !=-1) { value *=2; fprintf(out,"%hhd\n", value); fscanf(in, "%hhd", &value); } fclose(in); fclose(out); return(0); }
Repetiion/iteration structures
for, while, do while
Definition
These are loops that govern how many times a program will execute a certain task
Demonstration
/* * Sample code block */ #include <stdio.h> int main() { int v; while v!=0 { printf("Rise against the machines\n"); } else { printf(The machines have won\n") } return(0); }
Header Files
Libraries
Definition
These are the #include statements at the beginning of a program. They are needed so that certain commands can be understood by the compiler to run a program
Demonstration
#include <stdio.h> #include <stdlib.h> #include <math.h>
There are others but these are just a few
cprog Objective
cprog Objective
comprehend the basics of memory management, data representation and storage
Definition
Can the student understand how to allocate memory and represent what they wish to represent with the proper file type? Does the student understand how to store values in C?
Method
Explain the code of project 0
Measurement
The code of project 0 is defining the size of the storage available for the different types of arguments in C. Each storage size dictates how much memory needs to be allocated for that type and whether or not datat will fit into that storage type.
Analysis
I understand the logic behind most codes but will need to continue to work on writing the actual code.
Experiments
Experiment 1
Question
Can a program check the upper and lower bounds
Resources
Class notes and book
Hypothesis
Yes. The program can check the upper
Experiment
Write a code
Data
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
signed int input;
char column=0;
char row=0;
printf("Enter a value (0-4): ");
scanf("%d", &input);
while((input<4) && (input>0))
{
printf("argv[%hhu]: %c\n", input, *(*(argv+row)+column));
printf("You ran this program with %hhu arguments, they are:\n",argc);
exit(1);
}
printf("You have input an invalid value\n");
return(0);
}
Analysis
I know that the code should work but I am unable to get the right syntax to compile it.
Conclusions
I need to spend more time learning syntax.
Experiment 2
Question
What happens if you put a semicolon on the end of a loop statement
Resources
the book was consulted
Hypothesis
The program won't compile
Experiment
I will add a semicolon on the end of a loop statement in a program and see what happens
Data
The program didn't compile. The loop statement was treated like another regular statement in the program which threw the whole program off.
Analysis
The hypothesis was correct although I could have gone much further into figuring out why it would not compile. The hypothesis short cited and lacks depth.
Conclusions
Although the program behaved as expected it could have been explore further.
Experiment 3
Question
What types of things create a segmentation fault
Resources
class programs and book
Hypothesis
Faulty syntax will cause a seg fault
Experiment
Play with codes already written
Data
I found that mainly a logic error in the loops will give a seg fault
Analysis
Based on the data collected: The hypothesis was not entirely correct. The hypothesis was very vague as was the question posed. If The hypothesis could have been slightly more specific the experiment might have had a little more guidance.
Conclusions
The main cause of segmentation faults are logic errors but logic errors also lead to other types of problems within the program.
