Walked into the postal collection depot and even before I got to the glass counter Mr Postie was searching the usual shelf for my stuff. He suggested I might get a rubber stamp to save me having to keep signing for parcels.... Anyway in the parcel was my VERY LARGE book and disks for the DICE software from Obvious Implementations Corporation.. for the Amiga Personal Computer. Version 3 no less... For technical support Compuserve: Go Amigav DICE user manual for March 13th 1994. Here are some names for you.. Dave Baker, Matt Dillon, Andy Finkel, Bryce Nesbitt, John Mainwaring , Mark Schnell and John Toebes. ... reads like a who's who Amiga side early 90's Also in the batch was AmiTCP/IP by good old Village Tronic plus disks. ... Sana-II network device driver specification released by Commodore Amiga Networking Group.
Back to DICE tonight and a happy few hours with my Complete Amiga C book, which comes with a registered version of DICE. The four DD disks ( that's double density ) are copied as XDCC1-4 on the hard drive and an assign written to the user-startup. You are then ready to rock and roll. This book is great cus it assumes you know nothing. And so tonight I have been through: What Complete Amiga C will teach you How to use the book What is DICE Amiga libraries and includes Processors and memory Programming language Functions and sub-routines We then move on to the installation and preliminary usage... Tomorrow me thinks. Amazing to think this is all on a few DD disks. That's the great thing about the Amiga... it tends to do what's written on the tin... and no messing. Straight in at the deep end, and you pretty well get the whole package.
Lesson 1 THE EDITOR With DICE set up on the computer you can begin by calling up the DICE editor from the SHELL with the line dmeTook me a while to realise where the file example "hello" was and realised that everything I did was going into RAM:T so I copied the hello.c into RAM:T and called it up from there... cd RAM:T Using the F9 key saves the work in the editor. It is standard practice to add .c to the end of C source code files. To run the file enter run hello.c What is very useful is that you can run the editor and compiler together at the same time so that you can check then fix errors as you go along. To compile a program with DICE simply type dcc hello.c This will cause DICE to go off and compile and link your program, producing an executable. i.e. a runable program with the same name minus the customary .c. What happens when you fire this up from say DOPUS is that you get the ENTER ARGUMENTS for "hello" which on return executes the file. You can then make DICE produce an executable with a different name by using the -o option. dcc hello.c -o brian This will create an executable called brian If you just want to compile and not link this to an executable you just add -c option to the command line dcc -c hello.c This produces an object file called hello.o and if you want to compile a program and link it to a library you can type... dcc program.c hello.o -o program which will compile program and link it to library hello and produce and executable file - program.... Clear as mud. I now have a RAM T drawer full of hello.c, hello.o and hello files all doing different things. When you try to edit the execute it is filled with gibberish... The file hello.c had the lines #include main(ac, av) char *av[]; { puts("HELLO WORLD!"); } Which when executed stated simply HELLO WORLD! I think I am getting to understand matters.. We move on next to Basic C programming... Whoo hooooo.c or is it whoo hooo.o
Paul writes > #include> > main(ac, av) > char *av[]; > { > puts("HELLO WORLD!"); > } Danger, Will Robinson! K&R syntax alert! I guess this book is a little old... Or maybe I should say retro :-) K&R (Kernighan & Ritchie) invented the glorious C language. However, it's gone through a few revisions over the years. One of which is changing the way functions (like your 'main') is defined. The more proper way would be: int main (int ac, char **av) { puts("HELLO WORLD!"); } > Which when executed stated simply > > HELLO WORLD! > > > I think I am getting to understand matters.. > > We move on next to Basic C programming... > > Whoo hooooo.c or is it whoo hooo.o Well done! I suggest you work your way through the basic console stuff. It'll pretty much work on any platform, including Windows. If this book deals with Amiga GUI stuff and it's from the 1.3 era I'd avoid it and look for some kickstart 2.x tutorials, particular the gadtools.library. 1.3 was a real pain.
> This is the very very small program I > refer to in my next post... > > #include> > /* program to print a message on the screen */ > void main() > { > > printf("Hello from planet C\n"); > > } > > This one saved to Workbench for some reason. > When I execute it displays this ... > er... I saved the program as planet.c > then compiled it to become planet > > Hello from planet C > planet failed returncode 20 > > Why failed returncode 20 main() is a special function in C. It's where the program starts, and ends. On the Amiga main() should return a value to the caller (normally the CLI/Shell). So, if we change your program a little: #include /* program to print a message on the screen */ int main() { printf("Hello from planet C\n"); return 30; } Notice I changed the 'void' to 'int'. That's because 'void' means 'this function doesn't return anything' and 'int' means 'this function returns a number'.. It should now say planet failed returncode 30. You can use this return code. For example, suppose you wrote a program to detect if a mouse button was pressed or not. Pressed would return 5, not pressed 0. Stick this in your startup-sequence and the shell can take a special action, like run a command or something.
Tonight... Analysing a simple program You are prompted to run the editor and enter the following... #include/* program to print a message on the screen */ void main() { printf("Hello from planet C\n"); } The first line tells the compiler that we want to use some code that has already been written. This is collected in the ' header file ' The file is held within the angles brackets stdio.h Included for printing information on the screen The next line has to be left blank.. So far as white space this is all treated the same by C. It does not distinguish between a space character, a tab or return character. The next line is a comment. /* */ Anything between is ignored by the compiler After the comment comes the function definition The function is called main. Every C program has a function with this name. The computer must be told which function is first the top level or main. The word void before the word main indicates that the function does not produce a result. The parenthesis after the function name lets the compiler know that it is a function that is being defined. And the fact that there is no space between them indicates that the function does not require an input. The open and closed curly brackets bound the contents of the function. Reported speech must be enclosed in inverted commas. The statement that actually does something is printf. This is a pre written function that writes information to the screen. The f stands for formatted. Its definition is provided by the inclusion of stdio.h \n are instructions that tell printf to print a new line character Please note the semi colon at the end of printf This marks the end of the statement for the compiler. ... This can be the end of a block denoted by the closing curly brace. That's the end of my first program... Complicated or what.
Its fun with numbers tonight and variables. I got real stuck... cus the compiler kept throwing up errors on every line until I noticed I had put a full stop in the wrong place... duh ! #include/* program to total four numbers */ void main() { /* first declare variables */ int first, second, third, fourth, total; /* set the total value to zero */ total=0; /* now assign arbitrary values to the other variables, in a real-world example these values would be entered by the user running the program */ first=23; second=-5; third=42; fourth=1; /* now perform the addition to find the total */ total=total+first; total=total+second; total=total+third; total=total+fourth; printf ("The total is "); printf ("%d\n",total); } The line defining the variables could have been written: int first; int second; int third; int fourth; and in contrast the total could have been achieved by writing: total=total+first+second+third+fourth also the printf statement could have been written.. printf ("The total is %d in total",total; I am now getting my head around operator precedence in so much that the maths works from left to right unless multiplication is involved which takes priority. Struggling with 42%23 giving 19 at the moment, the remainder of 42 divided by 23. I appreciate why 42/23 gives 1 and not 1.826 but the 42%23 that's confusing. Operators are your times by, divided by, added etc This % modulus which finds the remainder... As I say I can't see how 42%23 makes 19... Next up floating point.
From the book...
If you try mixing several different operators
on the same line, you might notice some odd
results. For one thing, there is the
consequence of the integer division as
mentioned earlier, meaning that the expression
third/first (ie 42/23) would give the result 1,
rather than 1.826. To compensate for this
C provides an operator called the "modulus"
that will find the remainder. It is written
as a percentage sign and used just like the
operators already discussed. For example
the expression 42%23 would give the result 19,
the remainder of 42 divided by 23.
That last bit was the confusing bit.
I think however that you are right. If the
number was 88 and 88%23 applied I think the
result would be still 19... And yes if you
divide 88 by 23 and times the sum beyond
the decimal point by 23 you get 19. Its
a simple case of transposing equations.
Thank goodness for math...
> Struggling with 42%23 giving 19 at the moment, the > remainder of 42 divided by 23. I appreciate why > 42/23 gives 1 and not 1.826 but the 42%23 that's > confusing. > > Operators are your times by, divided by, added etc > This % modulus which finds the remainder... As I > say I can't see how 42%23 makes 19... > Idiots... Its not the remainder of 42 divided by 23... Its the remainder times 23. Cus of whole numbers 42 divided by 23 gives 1 and not 1.826. To compensate C creates the modulus which enables a figure to be achieved to represent this figure 42%23 which establishes the difference between the whole number and the fraction thereof, in this instance .826 and multiplies it by the 23 to give a value of 19. I get it now. I just logged that into the program and ran it and I do infact get 1 for 42/23 and 19 for 42%23. I am using Cygnus ED for writing my programs and then compiling with the SHELL with the command dcc i.e. dcc total.c I then check this by going into Dopus and executing the program. I am also using the Right-Amiga shortcuts a lot... RA-c copy RA-x cut RA-v paste dme in the SHELL gives the DICE editor. I prefer CED.
Moving on with Amiga C I am now into floating point and also linking the maths library. Floating point allows C to handle real numbers with as you would appreciate a floating point. This is defined by the keyword 'float' So now when we declare our variables we can add float to the statement. Note that any number that is assigned needs the decimal point. So 0 becomes 0.0 In the example below we also introduce the scanf which unlike the printf requires an input from the user... So you enter a number on request. To tell the scanf that it is dealing with a floating point variable we use "%f" and the second parameter to be stored must include the '&' The additional complication here is that when compiling you need to link the maths library. Now I mistook -lm to be -1m ( minus one m ) and I was an age sorting that out.... To compile you enter dcc float.c -lm -o float Where float is the name of the file you created... As below. You can call it anything. Then when you run the program you are asked to enter the values, and like magic the total is the sum there of... #include/* program to total four non-integer numbers */ void main() { /* first declare variables */ float first, second, third, fourth, total; /* set the total value to zero */ total=0.0; /* now get the numbers to be added from the user */ printf("Enter the numbers to be added\n"); printf("Enter the first number "); scanf("%f",&first); printf("\nEnter the second "); scanf("%f",&second); printf("\nEnter the third "); scanf("%f",&third); printf("\nEnter the fourth "); scanf("%f",&fourth); /* Now perform the addition to find the total */ total=total+first+second+third+fourth; printf("\nThe total is %f\n",total); } Well I am now at the end of that chapter... Next up ' Decision Making ' and reducing statements to true or false.
Time for decision making.... and more important the concept of true or false This time by example of a program for a simple calculator... #include/* simple calculator */ void main() { /* declare the variables */ float first, second, result; int reply; /* get the user to enter the numbers */ printf("Enter the two numbers to be opened on \n"); scanf("%f",&first); scanf("%f",&second); /* print up the menu and get the users choice */ printf("Which operation do you require?\n"); printf("1 - addition\n2 - subtraction\n3 - multiplication\n4 - division\n"); scanf("%d",&reply); /* now to make the decision */ switch (reply) { case 1: result=first+second; break; case 2: result=first-second; break; case 3: result=first*second; break; case 4: result=first/second; break; default: break; } printf("\nThe result is %f\n",result); } A statement can be true or false. The computer has no concept of being partially true. Therefore decision making is asking the computer if something is true. To establish this we enter a variable, which could be assumed as a reply. This is a variable under which the users input is stored. Imagine a simple calculator program as above where the user is asked to input two variables and then asked what to do with those variables... The 'switch ' statement means switch execution to one of the following groups of statements, depending on the result of the expression inside the parenthesis. The expression in this case is simply the variable 'reply'. Note that the body of the switch statement is in curly braces... this means that the body constitutes a statement block. Each of the lines beginning with case is an expression And so if the number following 'case' is the same as the variable inputted by the user the the statement following case is executed. We introduce here the concept of 'break' cus it tells the computer to break out of the switch statement and ignore all other statements in the block.... then to continue the next statement, in this case printf. Evidently you must include a break after default in the statement. Default is used to catch any unexpected result. In essence the switch is a good way of responding to a menu selection. As ever I created the above in CED then saved as calculator.c then I opened the SHELL and compiled dcc calculator.c -lm -o calculator And then I run from DOpus by simply clicking on the compiled file calculator. The name can be anything you want to call it.
Today I was looking at the IF statement and particularly the two == next to each other. #include/* Quick demo of if */ void main() { int reply; printf("Enter the code number\n"); scanf("%d",&reply); if (reply==999) printf("Correct\n"); } In this example the program tests whether the entered number is the same as the reply variable within the program. Simple enough. An equals sign on its own is used to store the result of an expression. Evidently confusing = and == is a common error. The comparison as a whole, made up as it is of two expressions and the test for equality ( known as a 'relationship operator ', since it examines the relationship between two expressions ) can also be viewed as an expression. This expression can have only one of two logical values. Either true or false. Falsity is represented by the number 0, any other number is equivalent to truth. .... Now the brain tickling statement.... In other words, you could substitute a simple expression for a logical one involving a relationship operator... Well that's your lot for February. Next DICE update will be March.
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Last updated 4th February 2007
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