There is a lot of overlap, so for example, “O3D” is the same as “O4d”. This makes it easier to write tunes without having the change octave all the time. Some of the notes in the lowest octaves (0 and 1) aren’t very accurate for technical reasons, and so the computer just makes regressive vs proportional vs progressive taxes a brave attempt at getting as close as possible. Notice also that the string a$ has been ‘built up’ by combining the two smaller strings o$ and n$. The duration is given in seconds, and the pitch is given in semitones above middle C (negative number for notes below middle C).
Calling +3DOS from BASIC
Note that in line 40 of this program, the two numbers following CODE are the address in memory of the start of the screen (16384) and the length of the top third of it (2048). By saving and loading only the top third, the overall speed is maintained. If you try to use any letter other than A, S or P in setting or resetting attributes, or if the ‘attribute string’ is not two characters long, then you will receive the report Invalid attribute. You can repeatedly switch attributes on or off without causing an error, so if you set write protect on a file that has already got write protection, it will just stay protected.
Example 1: bar graph axis with categorical data
Finally, the addition is carried out leaving the result 9. When the above program is run, the READ statement moves through the DATA list with each pass of the FOR…NEXT loop. You https://www.quick-bookkeeping.net/taxpayers-have-more-time-to-file-in-2017/ must be careful if you are running two FOR…NEXT loops together, one inside the other. Try this program, which prints out the numbers for a complete set of six dot dominoes.
- In order that each program file on a disk can be identified, you must give the program a filename when you save it.
- You can of course make back-ups onto tape, which may prove cheaper in the long run.
- A single track disk will not work in a double track drive, and vice versa.
- It has one argument – the port address, and its result is a byte read from that port.
The RAMdisk
This chapter describes the loading of commercially available pre-recorded tape software. If you wish to abandon a loading operation, simply press and release the RESET button. This chapter describes the loading of commercially available disk software. Again, using the cursor keys and ENTER, select the option Exit to return to the opening menu.
Low level floppy disk driving routines
CODE is applied to a string, and gives the code of the first character in the string (or 0 if the string is empty). An expression using AND or OR like this is called a conditional expression. If its value is 0, then it counts as false, and any other value (including the value of 1 that a true relation gives) counts as true.
ABS is another function whose argument and result are both numbers. It convert the argument into a positive number (which is the result) by forgetting the sign, so that for instance… Just as you can have different machines intangible asset to make different products – one for sausages, another for combs, a third for dish cloths, and so on, different functions will do different calculations. Each will have its own name to distinguish it from the others.
Finally, adjust the TV’s brightness, contrast and colour controls for the clearest display of the text characters within the colour bars. Connect the mains plug of the power supply unit to the mains supply socket, and switch on the socket-switch (if necessary). The power indicator lamp on the top panel of the +3 should illuminate.
In general, any instruction can be used as a command, and vice versa – it all depends on the circumstances. Every instruction or command must have at least one keyword. Keywords make up the vocabulary of the computer, and many of them require parameters. In the command DRAW 40,200 for example, DRAW is the keyword, while 40 and 200 are the parameters (telling the computer exactly where to do the drawing).
Notice that the letters A–F are listed along the top, and the numbers 1–6 are listed along the left edge. The general location of any item on this map can be found by using the letter and number of its grid square. For example, you can find the item that exists at square “4F” by moving your finger along the horizontal to https://www.quick-bookkeeping.net/ letter F and then straight down so you are in line with the 4. The -axis is the horizontal axis of a two-dimensional plot in Cartesian coordinates that is conventionally oriented to point to the right (left figure). In three dimensions, the -, -, and are usually arranged so as to form a right-handed coordinate system.
There is a function called ATTR that finds out what the attributes are at a given position on the screen. It is a fairly complicated function, so it has been relegated to the end of this section. Whilst typing into an INPUT request, the old Spectrum single-key entry system enjoys a brief moment of freedom before being locked away again when you press ENTER. At the bottom of the screen, and then you have to type in your age. In fact though, an INPUT statement can be made up of items and separators in exactly the same way as a PRINT statement, so How old are you?
Connections to the TAPE/SOUND socket are described in chapter 10. Here line 10 waits for you to life your finger off the keyboard, and line 20 waits for you to press a new key. A simple way of avoiding this problem is to evaluate the expression twice in succession and take the larger answer. This will draw a fairly decent line, even though it has gaps in it wherever it hits some writing. The line will vanish without leaving any trace whatsoever – this is the great advantage of OVER 1.
Soft-EOF is the character 1Ah (26) and is nothing to do with the EOF position, only the routine DOS BYTE READ knows about soft-EOF. There is a choice of action depending on whether or not the file already exists. The choices are ‘open action’ or ‘create action’, and are specified in DE. If the file already exists, then the open action is followed; otherwise the create action is followed.