Course: Computer Science. Module: 207SE Operating Systems, Security and Networks. Submission data: 3 rd March. Portfolio 1

Transcription

1 Name: Conor Flanagan Student id: Course: Computer Science Module: 207SE Operating Systems, Security and Networks Submission data: 3 rd March Portfolio 1

2 Lab Activity 1 Operating Systems Tasks and Programming a) In one paragraph describe what you feel the future of operating systems will be. You might include diagrams to support your predictions and describe how the future operating systems will differ from the current one. In the past, operating systems have been developed upon hardware available at the time of creation, needing to be rebuilt each time technology advanced (such as the development of integrated circuits over transistors), often causing prior data and systems to be unusable and obsolete (ComputerWorld 2003). The increase in significance and volume of data in today s world means that backwards compatibility is crucial for any new systems in order to preserve current data. In the future, the deceleration of software and hardware developments combined with streamlining of hardware means that OSes can and will build upon previous implementations; each new OS being a derivation of previous systems (like Android being a derivation of Linux, which in itself is derived from UNIX), primarily changing the method of interaction a user has with the system, while the background systems remain largely similar (Medium 2016). b) Programming activity (b1). def grammarcheck(): agent = ('bot', 'mike') action = ('pick','put','lift','drop','go') direction = ('forward','backwards','left','right') pronoun = ('I','you','we') objects = ('nuts','plum','cat','cup') colour = ('red','blue') initial = input("enter string to parse: ") wordlist = list() for w in initial.split(' '): #Split string into words using spaces to identify words wordlist.append(w) #Insert word at start of the list print(wordlist) #Print individual words as a list print(" ") while True: if wordlist[0] not in agent and wordlist[0] not in pronoun: print("grammar incorrect") break #If sentence does not start with an agent or pronoun else: if wordlist[1] not in action: print("grammar incorrect") break #If agent not followed by action else: if wordlist[2] not in objects and wordlist[2] not in direction and (wordlist[0] in pronoun and wordlist[2] in colour): print("grammar incorrect") break else: if wordlist[0] in agent and wordlist[2] in colour: if len(wordlist) <= 3: print("grammar correct") break elif wordlist[3] not in objects: print("grammar incorrect") break elif len(wordlist) <= 4: print("grammar correct") break else: print("grammar incorrect") elif len(wordlist) <= 3: print("grammar correct") break else: print("grammar incorrect") break print(" ") grammarcheck() if name == " main ": grammarcheck() #Run program again

3 Code output using example sentences provided:

4 Lab Activity 2 Linux Command Line (Commands and outcomes from a series of small tasks that require use of a number of Linux commands) a) Create a directory (Portfolio1) in home directory, make it read/write/executable for you and your group, executable for others. Show evidence with ls command. ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ mkdir Portfolio1 ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ chmod 711 Portfolio1 ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ ls lab2.txt [0m[01;34mPortfolio1[0m b) Download the script at to your home directory using wget and make it executable. ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ wget :44: Resolving ( Connecting to ( :80... connected. HTTP request sent, awaiting response Moved Permanently Location: [following] :44: Resolving centerkey.com (centerkey.com) Reusing existing connection to HTTP request sent, awaiting response OK Length: 2107 (2.1K) [text/plain] Saving to: â tree.shâ tree.sh 0%[ ] KB/s tree.sh 100%[==================================================================== ==============================================>] 2.06K --.-KB/s in 0s :44:19 (178 MB/s) - â tree.shâ saved [2107/2107] ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ chmod tree.sh x ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ mkdir bin ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ cd bin ]0;flanag20@hvs-its-lnx01: ~/binflanag20@hvs-its-lnx01:~/bin$ mv ~/tree.sh./ ]0;flanag20@hvs-its-lnx01: ~/binflanag20@hvs-its-lnx01:~/bin$ chmod 755 tree.sh c) Making Directories Create a 207se directory in your Portfolio1 directory. ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ cd Portfolio1 ]0;flanag20@hvs-its-lnx01: ~/Portfolio1flanag20@hvs-itslnx01:~/Portfolio1$ mkdir 207se Create numbered directories for the labs. i.e. lab1 and lab2 etc. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1flanag20@hvs-itslnx01:~/Portfolio1$ cd 207se ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207seflanag20@hvs-itslnx01:~/Portfolio1/207se$ mkdir lab1 ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207seflanag20@hvs-itslnx01:~/Portfolio1/207se$ mkdir lab2

5 Evidence of transferring lab1 activity into appropriate directory cd lab1 mv ~/Week1.docx./ Evidence of make directory activities using tree.sh tree.sh /home/207se/flanag20. -bin -Portfolio se -----lab lab2 d) Display todays date and using the cal command show the month that you were born. date Tue 28 Feb 16:46:12 GMT cal July 1997 Su Mo Tu We Th Fr Sa e) Move into the lab1 directory and use the appropriate command to show the current directory ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ cd ~/Portfolio1/207se/lab1 ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab1flanag20@hvs-itslnx01:~/Portfolio1/207se/lab1$ pwd /home/207se/flanag20/portfolio1/207se/lab1 f) What is talk, write and wall are for Wall Write a message to all users. Write Send a message to another user. Talk Talk with another user, even across different terminals. g) What command prevents the effects of those three commands from interrupting you.

6 h) Created a file called song.txt and entered a randomly generated song from Using wc count the number of words and lines in the file. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ wc song.txt song.txt Use grep to get the lines containing "and" and the number of the lines contain and in the document. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ grep and song.txt -n Output: Use cat to show the contents of the file. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ cat song.tc[kxt New life through me let me, with all my Soul no matter what they say the best doesn't mean Giving me the way you used to touch me and You'll succeed smile again just smile again just smile again Just smile again I'll always be there for You, gettin' it on the people Looked behind me, givin' it all For me need more and I can't even ask For more 'cause boy, you you are come As you are or where you're from come and Dance to the side, so I wanna Say thank you lord for showing me the way that I played around with love before I Never met no one loves you can Bring the world tonight, said the hearts of Stone, the only one for me Every part of me so baby, Baby the thought of no you cuts just Like yesterday you turned my life is full of Ecstasy where all you need and more and More see I finally know and you dont have to Makes lots of trust, and kissing and Holding you tight letting you know I'll Do what you need I found someone that's promise To be necessary to me I just Wanna be, you're so naughty and nice Hey they think I'm in need of love if I Was just a girl likes me never gonna Settle for less but if you got me coin' Craze boy, you lied you lied, you...

7 Replace any two words with your first and second names, save as song_name.txt. Use an appropriate command to see if and how they differ. differ song.txt song_name.txt 1c1 < New life through me let me, with all my --- > New life through me let Conor, with all my 25c25 < To be necessary to me I just --- > To be necessary to me Flanagan just Use sort to sort the file and redirect the output to a new file called song2.txt ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ sort song.txt > song2.txt Use sort and rev to reverse the sorted contents of song.txt and append the output to song2.txt ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ sort song.txt rev > song2.txt Total memory used and the total memory available ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ free -m total used free shared buff/cache available Mem: Swap: Display Name and Student ID on screen. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ echo Conor Flanagan Conor Flanagan Find out how you can display your username on the screen. ]0;flanag20@hvs-its-lnx01: ~/Portfolio1/207se/lab2flanag20@hvs-itslnx01:~/Portfolio1/207se/lab2$ echo "$USER" flanag20

8 List the processes that are running. ps -a PID TTY TIME CMD pts/82 00:00:00 less pts/70 00:00:00 pico pts/11 00:00:00 nano pts/11 00:00:00 nano pts/82 00:00:11 bochs-bin pts/3 00:00:00 bochs-bin pts/0 00:00:00 bash pts/0 00:00:01 bochs-bin pts/0 00:00:00 bash pts/0 00:00:00 bochs-bin pts/70 00:00:00 pico pts/49 00:00:00 man pts/49 00:00:00 man pts/49 00:00:00 pager pts/20 00:00:00 nano pts/8 00:00:00 pico pts/29 00:00:00 pico pts/67 00:00:00 pico pts/27 00:00:00 vi pts/16 00:00:00 script pts/36 00:00:00 ps pts/79 00:00:00 man pts/79 00:00:00 pager What are the differences between the Linux commands less, more and most. More Splits the output into individual screens which can be continued through using the spacebar. Less Like more, however provides a way to scroll back through previous pages. Most Can display more than one file at a time.

9 Lab Activity 4 Bootloader a) Brief description of the Lab activity and what you did: Booted pragma linux with bochs on the os-207se linux server. Created a bootloader using the helloworld.asm assembly code on moodle as a base. Bootloader (name.asm) displays name, address, favourite second year module, date of birth, age and student ID on separate lines. b) Boot pragma linux with bochs. ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ tar xvfz pragma- 207.tgz pragmalinux-img/ pragmalinux-img/readme pragmalinux-img/bootloader pragmalinux-img/a.img pragmalinux-img/bochsrc pragmalinux-img/bochsrc1 pragmalinux-img/bochsout.txt pragmalinux-img/testform.txt pragmalinux-img/bootloader.asm ]0;flanag20@hvs-its-lnx01: ~flanag20@hvs-its-lnx01:~$ cd pragmalinux-img ]0;flanag20@hvs-its-lnx01: ~/pragmalinux-imgflanag20@hvs-itslnx01:~/pragmalinux-img$ ls a.img bochsout.txt bochsrc bochsrc1 bootloader bootloader.asm README TESTFORM.txt c) Make a bootloader that displays your name, address, your favourite second year module, date of birth, age and student number on separate lines. Source code sensibly commented for your bootloader. (next page)

10 [BITS 16] [ORG 0X7C00] top: mov ax,0x0000 mov ds,ax mov si,name call writestring mov si, call writestring mov si,module call writestring mov si,dob call writestring mov si,age call writestring mov si,sid call writestring jmp $ ;Use writestring to display Name ;Use writestring to display ;Use writestring to display Module ;Use writestring to display Date of Birth ;Use writestring to display Age ;Use writestring to display Student ID writestring: mov ah,0x0e ;Display Character mov bh,0x00 mov bl,0x07 nextchar: lodsb cmp al,0 jz done int 0x10 jmp nextchar done: ret Name db 'Conor Flanagan',13,10,0 db 'flanag20@uni.coventry.ac.uk',13,10,0 Module db '210CT',13,10,0 Dob db '18/07/1997',13,10,0 Age db '19',13,10,0 sid db ' ',13,10,0 times 510-($-$$) db 0 ;Declaring values dw 0xAA55 Output from Bochs showing student details.

11 Lab Activity 6 Memory Management a) Determine. using first-fit, best-fit and worst-fit which unallocated memory blocks the process memory requirements will be allocated to, and prove using the.exe files provided. 1. Processes: Process 1 (300) Process 2 (350) Process 3 (450) Process 4 (400) Process 5 (150) Memory: Block 1 (300) Block 2 (500) Block 3 (250) Block 4 (220) Block 5 (270) First-fit method: Process 1 (300) allocated to Block 1 (300). Process 2 (350) allocated to Block 2 (500). Process 3 (450) cannot be allocated. Process 4 (400) cannot be allocated. Process 5 (150) allocated to Block 3 (250). First-fit.exe output: Results match my own determinations using the first-fit method.

12 2. Best-fit method: Process 1 (300): - Block 1 (300) difference: 0 - Block 2 (500) difference: Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 1 allocated to Block 1. Process 2 (350): - Block 2 (500) difference: Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 2 allocated to Block 2. Process 3 (450): - Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 3 cannot be allocated. Process 4 (400): - Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 4 cannot be allocated. Process 5 (150): - Block 3 (250) difference: Block 4 (220) difference: 70 - Block 5 (270) difference: 120 Process 5 allocated to Block 4. Best-fit.exe output: Results match my own determinations using the best-fit method.

13 3. Worst-fit method: Process 1 (300): - Block 1 (300) difference: 0 - Block 2 (500) difference: Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 1 allocated to Block 2. Process 2 (350): - Block 1 (300) does not fit. - Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 2 cannot be allocated. Process 3 (450): - Block 1 (300) does not fit. - Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 3 cannot be allocated. Process 4 (400): - Block 1 (300) does not fit. - Block 3 (250) does not fit. - Block 4 (220) does not fit. - Block 5 (270) does not fit. Process 4 cannot be allocated. Process 5 (150): - Block 1 (300) difference: Block 3 (250) difference: Block 4 (220) difference: 70 - Block 5 (270) difference: 120 Process 5 allocated to Block 1. Worst-fit.exe output: Results match my own determinations using the Worst-fit method.

14 First-fit and Best-fit allocate the processes with the least fragmentation, both leaving only 2 processes unallocated. b) Use first-in-first-out and random page allocation methods to show how pages will be swapped in and out of main memory for the examples. 1. First-in-first-out: Paging Accessing Sequence: Three table page entries: Page Entry Page Entry Page Entry Page Fault * * * * * * * * Page Fault Total: 8 Fifo.exe returns the same result: Four table page entries: Page Entry Page Entry Page Entry Page Entry Page Fault * * * * * * * * Page Fault Total: 8 Fifo.exe returns the same result:

15 2. Random page allocation: Three table page entries: Page Entry Page Entry Page Entry Page Fault * * * * * * * * * Page Fault Total: 9 Random.exe returns a different result because the victim pages are selected randomly, which can have a positive or negative impact. Four table page entries: Page Entry Page Entry Page Entry Page Entry Page Fault * * * * * * * Page Fault Total: 7 Random.exe returns a different result, again because the victim pages are randomly selected.

16 Lab Activity 7 Buffer a) Brief description of the Buffer Activity. Task is to first comment the buffer C code provided on moodle, then modify it, first to display error messages, then to display total characters read, characters read from the buffer, words in the document and times the buffer was filled. Finally a function added to compare the file with another, and if they are different display how. b) Commented Buffer.c code. #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h> #define BUF_SIZE 500 //Define buffer size at 500 #define OUTPUT_MODE 0700 //Define file permission int main(int argc, char *argv[]) { int in_fd, out_fd; int rd_size = 1, wr_size; char buf[buf_size]; //Declare buffer if (argc!= 3) exit(1); in_fd = open(argv[1], O_RDONLY); if (in_fd < 0) exit(2); //Open input file out_fd = creat(argv[2],output_mode); //Create output file if (out_fd < 0) exit(3); while (rd_size > 0) { rd_size = read(in_fd, buf,buf_size); //Read from input file to buffer if (rd_size <0) exit(4); wr_size = write(out_fd, buf, rd_size); //Write from buffer to output if (wr_size<=0){ close(in_fd); close(out_fd); //Close input and output exit(5);

17 c) Update the code to so that it prints if an error has occurred or if a file is successfully created with the content of the review in it. #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h> #define BUF_SIZE 500 //Define buffer size at 500 #define OUTPUT_MODE 0700 //Define file permission int main(int argc, char *argv[]) { int in_fd, out_fd; int rd_size = 1, wr_size; char buf[buf_size]; //Declare buffer if (argc!= 3){ printf("too many or too few arguments.\n"); exit(1); in_fd = open(argv[1], O_RDONLY); //Open input file if (in_fd < 0) { printf("given file is empty.\n"); exit(2); out_fd = creat(argv[2], OUTPUT_MODE); //Create output file if (out_fd < 0) { printf("file not created.\n"); exit(3); while (rd_size > 0) { rd_size = read(in_fd, buf, BUF_SIZE); //Read from input file to buffer if (rd_size <0) { printf("nothing to read from file.\n"); exit(4); wr_size = write(out_fd, buf, rd_size); //Write from buffer to output if (wr_size<=0){ close(in_fd); close(out_fd); exit(5); //Close input and output Contents of hamlet.txt:

18 d) Updated buffer.c code to show how many character are read to buffer, how many character read at a time into the buffer, how many words in the document and how many times the buffer is filled #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h> #define BUF_SIZE 500 //Define buffer size at 500 #define OUTPUT_MODE 0700 //Define file permission int main(int argc, char *argv[]) { int in_fd, out_fd; int rd_size = 1, wr_size; int characters = 0, filled = 0; int wordcount = 1, loop; char buf[buf_size]; //Declare buffer if (argc!= 3){ printf("too many or too few arguments.\n"); exit(1); in_fd = open(argv[1], O_RDONLY); //Open input file if (in_fd < 0) { printf("given file is empty.\n"); exit(2); out_fd = creat(argv[2], OUTPUT_MODE); //Create output file if (out_fd < 0) { printf("file not created.\n"); exit(3); while (rd_size > 0) { rd_size = read(in_fd, buf, BUF_SIZE); //Read from input file to buffer if (rd_size <0) { printf("nothing to read from file.\n"); exit(4); if (rd_size==500) { //If rd_size is 500 characters = characters + 500; //Add 500 to char count filled = filled + 1; //Add 1 filled buffer else{ characters = characters + rd_size; //Else add rd_size to char count for (loop = 0; loop < rd_size; loop++){ if (buf[loop] == ' '){ //If char is space add to word count wordcount = wordcount + 1; else if (buf[loop] == '.'){ //If char is space add to word count wordcount = wordcount + 1; loop = loop + 1; //Next char likely ' ' so skip wr_size = write(out_fd, buf, rd_size); //Write from buffer to output if (wr_size<=0){ close(in_fd); close(out_fd); //Close input and output printf("character count: %d\n", characters); printf("word count: %d\n", wordcount); printf("buffers filled: %d\n", filled); exit(5);

19 Output of updated code: e) Alter buffer size and explain how this influences the number of times the buffer is filled. When the buffer size is increased, the buffer is filled less often. This means there is less of an overhead when filling the buffer and so the operation takes less time. f) Adapt the code in buffer.c so it is possible to compare two files and determine if they are the same. If they are different explain how they differ. #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h> #define BUF_SIZE 500 //Define buffer size at 500 #define OUTPUT_MODE 0700 //Define file permission int compare(char *File) //Compare with another file { int in0fd, in1fd; char comparefile[50]; int rd_size0 = 1, rd_size1 = 2; char buf0[buf_size], buf1[buf_size]; int loop, bool=0; char q; printf("file to compare? "); //Ask for second filename scanf("%s", comparefile); in0fd = open(comparefile, O_RDONLY); in1fd = open(file, O_RDONLY); if (in0fd<0) { printf("given file is empty.\n"); //Exit if file is empty exit(6); while (rd_size0 > 0) { rd_size0 = read(in0fd, buf0, BUF_SIZE); //Read each file rd_size1 = read(in1fd, buf1, BUF_SIZE); //into each buffer if (rd_size0 <0) { printf("nothing to read from file.\n"); exit(4); if (rd_size1 <0) { printf("nothing to read from file.\n"); exit(4); for (loop = 0; loop < rd_size0; loop++) { q = buf1[loop]; if (buf0[loop]!= q) { //Compares characters in each buffer if (bool == 0) printf("file differs with characters: \n"); printf("%c", q); //Prints characters that differ

20 bool = 1; printf("\n"); if (bool == 0) //Declare if files are identical printf("files are the same.\n"); int main(int argc, char *argv[]) { int in_fd, out_fd; int rd_size = 1, wr_size; int characters = 0, filled = 0; int wordcount = 1, loop; char buf[buf_size]; //Declare buffer char cmpr[1]; if (argc!= 3){ printf("too many or too few arguments.\n"); exit(1); in_fd = open(argv[1], O_RDONLY); //Open input file if (in_fd < 0) { printf("given file is empty.\n"); exit(2); out_fd = creat(argv[2], OUTPUT_MODE); //Create output file if (out_fd < 0) { printf("file not created.\n"); exit(3); while (rd_size > 0) { rd_size = read(in_fd, buf, BUF_SIZE); //Read from input file to buffer if (rd_size <0) { printf("nothing to read from file.\n"); exit(4); if (rd_size==buf_size) { //If rd_size is 500 characters = characters + BUF_SIZE; //Add 500 to char count filled = filled + 1; //Add 1 filled buffer else{ characters = characters + rd_size; //Else add rd_size to char count for (loop = 0; loop < rd_size; loop++){ if (buf[loop] == ' '){ //If char is space add to word count wordcount = wordcount + 1; else if (buf[loop] == '.'){ //If char is space add to word count wordcount = wordcount + 1; loop = loop + 1; //Next char likely ' ' so skip wr_size = write(out_fd, buf, rd_size); //Write from buffer to output if (wr_size<=0){ close(in_fd); close(out_fd); //Close input and output printf("character count: %d\n", characters); printf("word count: %d\n", wordcount); printf("buffers filled: %d\n", filled); printf("compare file with another [yes/no]? "); scanf("%s", cmpr); if (cmpr[0]=='y'){ compare(argv[2]); exit(5);

21 Comparison of review.txt and hamlet.txt Comparison of hamlet.txt and review_observer.txt

22 Lab Activity 8 Cache Buffer a) Brief Description of Cache Buffer Activity. Alter the cache-buffer file provided so that it outputs the bytes to the screen, then alter further to prove that the output is being buffered, and display statistics including byte count and buffer count. b) Commented implementation of the cr_read_byte function. char cr_read_byte(cr_file* f){ char curbyte; //Character for current byte if (f->usedbuffer >= f->bufferlength){ refill(f); //If buffer is empty refill else{ curbyte = f->buffer[f->usedbuffer]; //Assigns current byte to character f->usedbuffer += 1; //Increases buffer pointer by 1. return curbyte; //Returns current byte character return EOF; Output (some file text cropped to the side for visibility): Explanation: Checks if the usedbuffer pointer is past the end of the buffer length. If so, calls the refill function to refill the buffer and reset the usedbuffer pointer. If not, increases the pointer by 1 and returns the byte the pointer was at. Char variable is used so that the pointer can be increased before the return statement without returning the incorrect (the next) byte.

23 c) Additional tasks 1 and 2: Prove the file output is being buffered, and provide statistics for bytes read in total and times buffer was refilled. Declaration line added to cache_reader.h library: int totalbytes; //Stores total amount of bytes from file cache_reader.c with changes highlighted: #include "cache_reader.h" int refill(cr_file* buff){ //Refills a buffer //Only works when completely used buffer if(buff->usedbuffer!=buff->bufferlength) return 0; else{ buff->usedbuffer=0; int len=fread(buff->buffer, sizeof(char), buff->bufferlength, buff->file); //If we didn't fill the buffer, fill up with EOF if(len<buff->bufferlength) for(int i=len;i<buff->bufferlength;i++) buff->buffer[i]=eof; //Accessing like an array! buff->totalbytes += len; //Add len to total byte count return len; void cr_close(cr_file* f){ free(f->buffer); fclose(f->file); cr_file* cr_open(char * filename, int buffersize){ //Info on malloc // FILE* f; if ((f = fopen(filename, "r")) == NULL){ fprintf(stderr, "Cannot open %s\n", filename); return 0; cr_file* a=(cr_file*)malloc(sizeof(cr_file)); a->file=f; a->bufferlength=buffersize; a->usedbuffer=buffersize; //Start off with no characters, so refill will work as expected a->buffer=(char*)malloc(sizeof(char)*buffersize); a->totalbytes=0; //Start byte total at 0 refill(a); return a; // char cr_read_byte(cr_file* f){ char curbyte; //Character for current byte if (f->usedbuffer >= f->bufferlength){ printf("\n"); //Separates each buffer refill to individual lines refill(f); //If buffer is empty refill else{ curbyte = f->buffer[f->usedbuffer]; //Assigns current byte to character f->usedbuffer += 1; //Increases buffer pointer by 1. return curbyte; //Returns current byte character return EOF;

24 cache_example.c with changes highlighted: #include "cache_reader.h" //Simple file display to show how easy it is to use the cached reader functions int main(){ char c; //Open a file cr_file* f = cr_open("text",20); //While there are useful bytes coming from it while((c=cr_read_byte(f))!=eof) //Print them printf("%c",c); //Then close the file printf("\ntotal Bytes: %d",f->totalbytes); //Prints total byte count. printf("\ntotal Refills: %d",f->totalbytes/f->bufferlength); //Prints total number of refills performed. printf( \n ); cr_close(f); //And finish return 0; Output:

25 Lab 10: The Cache Buffer from week 8 with system calls a) Brief description of the activity Change cache_reader.h library from using fopen, fread and fclose functions to use the system call versions (open, read, close). Also remove effects of caching on the library. b) Changes the cache_reader library from using the fopen, fread, fclose functions to the system call versions open, read, close. #include "cache_reader.h" #include <fcntl.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> int refill(cr_file* buff){ //Refills a buffer //Only works when completely used buffer if(buff->usedbuffer!=buff->bufferlength) return 0; else{ buff->usedbuffer=0; int len=read(buff->file, buff->buffer, buff->bufferlength); //If we didn't fill the buffer, fill up with EOF if(len<buff->bufferlength) for(int i=len;i<buff->bufferlength;i++) buff->buffer[i]=eof; //Accessing like an array! buff->totalbytes += len; //Add len to total byte count return len; void cr_close(cr_file* f){ free(f->buffer); close(f->file); cr_file* cr_open(char * filename, int buffersize){ FILE* f; if ((f = open(filename, O_RDONLY)) < 0){ //Changed == NULL to < 0 fprintf(stderr, "Cannot open %s\n", filename); return 0; cr_file* a=(cr_file*)malloc(sizeof(cr_file)); a->file=f; a->bufferlength=buffersize; a->usedbuffer=buffersize; //Start off with no characters, so refill will work as expected a->buffer=(char*)malloc(sizeof(char)*buffersize); a->totalbytes=0; //Start byte total at 0 refill(a); return a; No changes were made to cache_reader.h Output is the same as running previously. Screenshot on next page.

26 c) Changes cache_reader library to remove (as far as possible) the effects of caching on the library. References D. Gelernter, ComputerWorld (2003) Future of operating systems: simplicity [online] available from < R. Rosini, Medium (2016) AI and the Future of Operating Systems [online] available from