When the virus is run, it infects the first uninfected DOS executable by writing itself to the beginning of the file. It ignores files smaller than the virus itself.
When the user attempts to run the very first infected program, the virus decrypts and overwrites it with the payload code, which would appear a lot of various colorful lines of the text:
Some of the colorful lines would have a flashing effect.
On further execution of the overwritten program will always activate the virus and will not run the host program anymore.