Mention 3 free sites to learn hardware software and firmware ?

-comment ca marche

-pc astuce

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https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwiN6tDtxOnPAhXCVxQKHQCQCYAQFgg5MAU&url=http%3A%2F%2Fwww.onlinediploma.pk%2Fcourse.php%3Fid%3D44&usg=AFQjCNGsa7q7QRvnyKfVvqgeUQw-ZqVHUQ&bvm=bv.136499718,d.d24

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiN6tDtxOnPAhXCVxQKHQCQCYAQFgg-MAY&url=http%3A%2F%2Fwww.onlinediploma.pk%2F&usg=AFQjCNGsg3x2DO-9uh426I-HcPBYzrvsxg&bvm=bv.136499718,d.d24

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwiN6tDtxOnPAhXCVxQKHQCQCYAQFggzMAQ&url=http%3A%2F%2Fcs.sru.edu%2F~mullins%2Fcpsc100book%2Fmodule02_introduction%2Fmodule02-03_introduction.html&usg=AFQjCNHhhmk5qppRDP1xzWPwi_X-NwAyEw&bvm=bv.136499718,d.d24

you go on google  and type your query from there you can select or else on youtube you can learn form video , that is illustrate by expert in every topicwise , from there you can access their private poratl given by the tutor.