When you enter a command you type its name at the prompt, followed by a space and any parameters for the command. For example, all of these could be valid commands:
[c:\] dir [c:\] copy file1 file2 d:\ [c:\] f:\util\mapmem /v [c:\] "c:\my programs\jp software\take command\tcmdos2.exe" /l
The last three commands above include both a command name, and one or more parameters. There are no spaces within the command name (except in quoted file names), but there is a space between the command name and any parameeters, and there are spaces between the parameters.
Some commands may work when parameters are entered directly after the command (without an intervening space, e.g. dir/p), or when several parameters are entered without spaces between them (e.g. dir /2/p). A very few older programs may even require this approach. However leaving out spaces in this way is usually technically incorrect, and is not recommended as a general practice, as it may not work for all commands.
If the command name includes a path, the elements must be separated with backslashes (e.g. f:\util\mapmem). If you are accustomed to Unix syntax where forward slashes are used in command paths, and want CMD.EXE to recognize this approach, you can set UnixPaths to Yes in CMD.INI.
For more information on command entry see Multiple Commands and Command-Line Length Limits. For details on how CMD.EXE handles the various elements it finds on the command line see Command Parsing.