why IBM hired Microsoft/Intel

makhan10 said:

i dont understand why IBM hired Microsoft and Intel

why IBM ditnt write their OS and made their own chips

You might want to watch this nice video from LGR.

IBM did have a competing DOS/Disk Operating System against Microsoft's back in the '80s and '90s. That was a choice I had to decide on with my first computer which was an AMD 80386/40MHz CPU, 4MB RAM, 120MB HDD running MS-DOS 5 with Windows 3.1 on it. Back then Windows was more of a GUI/Graphical User Interface, both installed separately, DOS first then Windows on top of it. Later both began coming together starting with Win95.