what is the name of desert name at west side of south america. and at northern side of africa
Check these maps.
https://www.cia.gov/library/publications/the-world-factbook/reference_maps/south_america.html
http://www.worldatlas.com/webimage/countrys/aflnd.htm
The desert at the west side of South America is called the Atacama Desert. To find the answer to this question, you can use an internet search engine like Google or Bing and type in "desert at west side of South America" or a similar query. You will easily find information about the Atacama Desert.
The desert at the northern side of Africa is called the Sahara Desert. Similarly, you can use the same search method to find the answer by typing in "desert at the northern side of Africa" or related keywords into a search engine, and you'll discover information about the Sahara Desert.