100 marks come from science and computer in BCS written exam. Science is like math. That is, if you answer correctly, you will get full marks. How to take BCS written preparation in these subjects, I will know in detail.

First check the syllabus.
In short,
General Science- 60 marks.
Computer and Information Technology- 25 marks.
Electrical and Electronic Technology- 15 marks.
I am giving the detailed syllabus.    BCS Written Preparation: General Science Syllabus 1. Light: Nature, spectrum, different colors and wavelengths, UV, IR, and lasers, reflection of light, refraction of light, total internal reflection of light, lenses, thin converging lenses, diffraction of light, particle nature of light, Einstein's photoelectric equation, photocell.

2. Hearing process, decibels, frequency, sound machines in and around the home -, microphones, loud speakers, public address systems, characteristics of a sound note, formation of standing waves in stretched strings, laws of vibrating strings, beats, Doppler effect , applications and limitations of Doppler effect, echoes, wave sound absorption, reverberation, fundamentals of building acoustics, statement of Sabin's law.

3. Relation to polarity and current, bar magnet, magnetic lines of force, torque magnetic field on a bar magnet, earth's magnetic field as a bar magnet, tangent galvanometer, vibrating magnet instrument, para, dia and ferromagnetic materials with examples, electromagnets and permanent magnets.

4. Acid-base concept, properties of acids and bases, acid-base index, uses of acids and bases. Daily life and precautions in managing them, social impact of acid abuse, causes and selection of acidity in stomach. Correct food, pH , measurement and importance of pH of substances, salt, properties of salt, need of salt in daily life, use of salt in agriculture and industry.

5. Properties of water, melting and boiling point of water, electrical conductivity, structure of water, hydrogen bonding. Sources of water, sources of fresh water in Bangladesh, parameters of water quality (color and taste, turbidity, presence of radioactive substances, presence of waste. Dissolved oxygen, temperature, pH and salinity), recycling of water, role of water in nature conservation, requirement of quality water, water purification ( Filtration, Chlorination, Boiling and Distillation), Causes of Water Source Pollution in Bangladesh, Effects of Water Pollution on Plants, Animals and Humans. Pure warming effects on fresh water, water pollution prevention strategies and citizen responsibility or public awareness, of water pollution by industry, prevention of water pollution due to prevention soil erosion from agricultural land, conservation and development of water sources.

6. Soils, soil types, soil pH, causes and effects of soil pollution, sources of natural gas, petroleum and coal, forestry, limitations and conservation of our resources.

7. Biosphere and hydrosphere, ionosphere, role of oxygen, carbon dioxide and nitrogen. Drinking and contaminated water, pasteurization.

8. Food Ingredients, Carbohydrates, Proteins, Fats and Lipids, Vitamins, Types and Sources of Carbohydrates, Proteins, Nutritional Value, Balanced Food Menu, Balanced Food Pyramid, Body Mass Index (BMI), Fast Food or Junk Food, Food Preservation, Different Types of Food Preservation Processes, use of chemicals for food preservation and its effects.

9. Chromosomes, shape, structure and chemical composition of chromosomes, acids, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), proteins, genes, DNA testing, forensic testing, genetic disorders in humans, biotechnology and genetic engineering. Cloning, Social impact of cloning, Transgenic plants and animals, Uses of biotechnology. Agriculture, milk products and pharmaceuticals, gene therapy, genetically modified organisms, nanotechnology, pharmacology, pharmacokinetics.

BCS Written Preparation: General Science Booklist
Oracle Science Guide.

1) There is no comparison to this book. You will not find a better book in the market. All subjects of science are well analyzed. Read this book alone.

2) 8th, 9-10th and higher secondary books should be read. All syllabus topics are taken from these classes. So read each topic from these books.

3) Previous Year Question Solution Guide. You can take any one.

BCS Written Preparation: Computer and Information Technology Booklist 1) Guide to Easy Publishing.  This book is better than other books. Or you can buy books from professors

2) Higher Secondary Board Book.  Buy books by two authors. Mahbubur Rahman Sir and Mujibur Rahman Sir. Read the book of these 2 people. Note every topic from the syllabus. Then match the book with the topic. Start reading.