OK, you have so much to learn.
The commands are not the letters arranged into words, it is actual tokenized commands. You can see them in the menus, or press 2nd and 0 for almost every command you need in the Command Catalog if you can't find it.
To find Disp, you can do one of 2 things:
1. Press Prgm, right, and arrow down to Disp, or
2. Press 2nd, then 0, then press the (x^-1) button to go down to D, then scroll down to Disp.
Then, press enter to add it to the program.
The reason you got a syntax error is the calculator, because of the syntax of what you put in, thought you wanted to multiply variables D, I, S, and P. It then sees a space, and since you can't multiply a number by a space, it gives a syntax error.
So in the meantime, do not enter commands that way. Go through the menus, or the Command Catalog to do it.
P.S. You spelled WORLD wrong.